Abstract:
Electric plugs or connectors are provided where protruding prongs are protected or reinforced by a brace element or configured to be readily replaceable. The brace element is used to buttress the prongs when the plug is not plugged into an electric receptacle. The brace element is configured to be deployed either manually or automatically.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority of U.S. Provisional Patent Applications No. 61/460,689, filed Jan. 6, 2011; No. 61/574,828, filed Aug. 10, 2011; and No. 61/630,000, filed Dec. 2, 2011, which are hereby incorporated herein by reference in their entirety. 
    
    
     FIELD OF INVENTION 
     The present invention generally relates to electrical connectors with protruding prongs that are used to connect to a receptacle that receives the prongs. In particular, it relates to the protection of such prongs from damage or the facilitating of their replacement when damaged. 
     BACKGROUND 
     Home appliances, power tools, space heaters, and other equipment that consume electric power are ubiquitous in society. In order to operate properly, such devices frequently rely on electrical connectors or plugs to connect to an alternating or direct current source. Such connectors frequently utilize protruding prongs of various shapes and lengths that, in use, are intended to mate with matching receiving terminals of a receptacle. Such prongs are typically supported only at one end, i.e. at the point of attachment to the plug base. They necessarily act as cantilever beams if and when they are exposed to forces or components of forces that are perpendicular to their longitudinal axes. The common two or three prong 110/120 volt alternating current plugs are examples of such connectors. They are typically used to supply AC power to various types of apparatus. Such plugs typically comprise a molded plug base with two or three protruding prongs embedded in the base on one side and a cord or cable, with two or three conductors, attached to another side of the plug base. The plug base is frequently fabricated by encapsulating the electrical connections, between the prongs and the conductors in the cord, in a plastic material to form a rugged and durable unitary piece. Typically, overmolding and/or insert molding processes are used. The 110/120 volt AC plugs, in common use in the USA, have two substantially flat or blade prongs. When plugged into a receptacle, these flat prongs act as the line voltage and neutral connections. A third prong that is substantially in the shape of a circular cylinder is typically added for safety and connects to the ground lead in a receptacle. Other types of alternating and direct current electrical connectors or plugs, that are in use worldwide, have various numbers of prongs of various shapes and purposes. 
     The prongs of such connectors are typically positioned and oriented as necessary to properly mate with the matching receptacles. The spacing of the prongs and the materials used in the fabrication of the plug have to be such as to avoid the excessive leakage of current and minimize the risk of a short circuit. The prongs are also sufficiently spaced from the outer edges of the plug base to reduce the chance of electrical shock and also to help maintain the physical integrity of the plug base. 
     Plugs, especially those utilized in a commercial or industrial environment such as, for example, a construction site, are frequently exposed to rough usage. Such plugs may be attached to, for example, the cord of an electric tool or apparatus or an extension cord. Typically the plug base and the cord are rugged enough to withstand such usage with little ill effect. When the prongs are fully engaged in a receptacle, they too are usually well protected from damage. However, when not in use, plugs are frequently left exposed, for example, on the floor of a construction site. Under such circumstances, the prongs are frequently damaged by forces that cause them to bend and twist. For example, prongs are frequently crushed when they are stepped on, run over by wheels of various pieces of equipment or hit by, for example, dropped tools or other heavy objects. They are, therefore, frequently bent and deformed. They then have to be straightened and untwisted so that they may be plugged into a receptacle. 
     Repeated bending and straightening is not only a nuisance, but can be dangerous. Frequently, metal prongs fatigue and break off after repeated bending. Under such circumstances, the entire cord or at least the plug needs to be replaced even though the plug base and the cord are completely sound. Even when the plug alone is replaced, it is still an added expense and a nuisance. Typically the electric cord must be cut to separate the damaged plug and the cord. The conductors in the cord have to then be stripped and attached to what are typically screw terminals in a replacement plug. Replacement plugs are typically not as rugged or robust as original injection molded plugs. Also, since they are typically installed by non-electricians, use of replacement plugs increases the risk of causing a short circuit, damaging equipment, and even causing injury or electrocution. 
     In certain circumstances, especially in the case where only the ground prong breaks off, the plug is used with a missing prong, which increases the likelihood of malfunction, and the danger of electrocution, personal injury or damage to equipment. Prongs that have been repeatedly bent cannot be fully straightened and as a result frequently do not fit properly in a receptacle and can damage the receptacle as well. Examples of electrical connectors are disclosed in U.S. Pat. Nos. 5,320,560 and 5,567,175, the contents of which are incorporated herein by reference in their entirety. 
     SUMMARY OF INVENTION 
     One object of the present invention is to protect exposed, protruding prongs of an electric plug or connector, from being crushed or otherwise damaged, for example, by being stepped on. 
     In an embodiment according to the invention, an electric plug or connector is configured to include an integral brace element for buttressing the prongs of the plug. The brace element may be withdrawn to allow the plug to be received normally in a receptacle. When the plug is not engaged in a receptacle, the brace element may be deployed to augment the degree to which at least one prong is supported. It is preferred that the brace element buttress and shield the prongs. 
     In another embodiment according to the invention, an electric plug or connector is configured to include an integral deployable shield for protecting the prongs of the plug. 
     It is preferred that the brace element both support and shield the prongs of a plug when it is deployed. More preferably, the brace element is an integral element of the plug that is slidably attached to at least two prongs and the plug base. It is yet more preferable that when the brace element is fully deployed, at least two prongs are buttressed against lateral movement by being securely bound together by the brace element at a point at or near their distal ends. 
     The brace element or shield may be deployed manually after the plug is withdrawn from the receptacle. Alternatively, the brace element or shield may be deployed automatically by an actuator when the plug is withdrawn. 
     In another embodiment according to the invention, the brace element is configured as a dummy receptacle which may be attached to, for example, the plug or its cord. The dummy receptacle may be attached to the plug or to its cord by using, for example, elastic straps, screws, snaps, sleeves, collars and/or adhesives. The dummy receptacle may be configured to shield and/or support and buttress the protruding prongs of a plug and not to supply electricity. For example, an extension cord may be configured comprising a three prong male connector at one end, a female plug with one or more sets of receiving terminals at the other end, and a dummy receptacle attached to the cord. It is preferred that the dummy receptacle be flexibly attached, to the electric cord, in close proximity to the male plug or to the male plug itself. When attached to the cord, it is preferred that the point of attachment be less than or equal to approximately one foot from the male plug. It is yet more preferred that the point of attachment be less or equal to approximately one inch from the male plug. 
     The plug may be plugged into the dummy receptacle when it is withdrawn from an electric receptacle so that the prongs are protected. It is preferred that when the prongs are engaged in a dummy receptacle at least one prong is supported and protected along its entire length. It is preferred that the outer dimensions of the dummy receptacle, in the transverse direction, closely approximate those of the plug. Therefore, when the plug is plugged into the dummy receptacle, preferably a smooth transition would occur between the outer dimension of the plug and that of the dummy receptacle. It is still further preferred that the outer envelope of the cross section of the plug be approximately a minor image of that of the dummy receptacle about the plane where the two are joined. 
     Another object of this invention is to retrofit a conventional plug with a detachable plug adapter that is fitted with an integral brace element that is configured to support and/or protect the prongs of the adapter when the brace element is deployed. The prongs of the conventional plug are simultaneously protected by being plugged into corresponding receiving terminals of the plug adapter. It is preferred that the adapter be attached to the conventional plug by a positive attachment device such as, for example, a screw. 
     The brace element of the adapter may be deployed manually after the adapter is withdrawn from the receptacle. Alternatively, the brace element may be deployed automatically by an actuator when the adapter is withdrawn from a receptacle. 
     It is a further object of this invention to facilitate the replacement of damaged prongs of an electrical plug so that it may be performed inexpensively and quickly, even by non-electricians. 
     In still another embodiment according to the invention, an electric plug is configured such that it comprises two readily separable mating pieces. One of these mating pieces, the prong assembly, comprises two or more prongs, each of which is electrically connected to a terminal or electrical contact. It is preferred that the prong assembly be fabricated by an injection molding process that encapsulates the electrical connections between each prong and its corresponding terminal. 
     The second of the mating pieces, the plug base, comprises connections between conductors within the electrical cord with the corresponding electrical terminals or contacts. The terminals in the two pieces of the plug are configured such that, when the constituent pieces of the plug are attached together, the corresponding terminals of the constituent pieces of the plug make electrical contact such that each prong in the prong assembly is electrically connected to a corresponding conductor in the electrical cord. It is preferred that the plug base be fabricated by an injection molding process that encapsulates the connections between each of the conductors in the electrical cord and the corresponding plug base terminal. 
     In yet a further embodiment according to the invention, a plug or a plug adapter is configured which comprises individually removable prongs that may be easily replaced by an untrained person if any such prong is damaged. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  shows a schematic of a perspective view of a three prong plug configured according to an embodiment of the invention comprising a brace element in a retracted position. 
         FIG. 2   a  shows a schematic of a perspective view of the plug in  FIG. 1  with the brace element in a deployed position. 
         FIG. 2   b  shows a schematic of an orthogonal end view of the brace element shown in  FIG. 1  and  FIG. 2   a.    
         FIG. 2   c  shows a schematic of an orthogonal side view of the brace element shown in  FIG. 1 ,  FIG. 2   a  and  FIG. 2   b . The brace element is shown in section. 
         FIG. 3   a  shows a schematic of a perspective view of a three prong plug, configured according to another embodiment of the invention, with a brace element in a retracted position. 
         FIG. 3   b  shows a schematic of a perspective view of the plug in  FIG. 3   a  with the brace element in a deployed position. 
         FIG. 3   c  shows a schematic of an orthogonal end view of the brace element shown in  FIG. 3   a  and  FIG. 3   b.    
         FIG. 3   d  shows a schematic of an orthogonal side view of the brace element shown in  FIG. 3   a ,  FIG. 3   b  and  FIG. 3   c . The brace element is shown in section. 
         FIG. 3   e  shows a schematic of a perspective view of a three prong plug, configured according to a further embodiment of the invention, comprising a brace element with a protrusion that is received in a recessed channel along a prong. 
         FIG. 3   f  shows a schematic of a perspective view of the plug in  FIG. 3   e  wherein the brace element is in a fully deployed position. 
         FIG. 3   g  shows a schematic of a perspective view of a three prong plug configured according to yet another embodiment of the invention comprising a brace element with a screw, the tip of which is received in a recessed channel along a prong. 
         FIG. 3   h  shows a schematic of an orthogonal sectioned end view of the brace element in  FIG. 3   g.    
         FIG. 4   a  shows a schematic of a perspective view of a three prong plug and plug adapter, configured according to still another embodiment of the invention, comprising a brace element in a retracted position. 
         FIG. 4   b  shows a schematic of the plug and plug adapter of  FIG. 4   a  with a brace element in a deployed position supporting, buttressing and shielding the three prongs of the adapter. 
         FIG. 5   a  shows a schematic of a plug configured according to a further embodiment of the invention. The brace element is shown in section in a fully retracted position. The brace element is slidably attached to the plug base. 
         FIG. 5   b  shows a schematic of the plug in  FIG. 5   a  where the brace element has been deployed fully to support, buttress and shield the prongs. The brace element is slidably attached to the plug base. 
         FIG. 5   c  shows a schematic of another brace element without a web-plate configured according to an aspect of an embodiment of the invention. 
         FIG. 5   d  shows a schematic of a brace element configured according to an aspect of an embodiment of the invention. The brace element is shown in section, comprising multiple distinct pieces that may be made of various materials. The brace element is a unitary assembly of multiple pieces that is slidably attached to the plug base. 
         FIG. 5   e  shows a schematic of an orthogonal side view of a plug in partial section with a brace element configured, according to a still further embodiment of the invention. 
         FIG. 5   f  shows a schematic of the plug in  FIG. 5   d  where the brace element has been deployed fully to buttress the prongs. 
         FIG. 6   a  shows a schematic of a plug and plug adapter, which comprises a brace element, configured according to still another embodiment of the invention. The brace element and the plug adapter base are shown in section and partial section respectively. 
         FIG. 6   b  shows a schematic of the plug and plug adapter of  FIG. 6   a  with the brace element deployed fully to support, buttress and shield the prongs of the plug adapter. The brace element is slidably attached to the adapter base. 
         FIG. 7   a  shows a schematic of a plug and a dummy receptacle configured according to yet another embodiment of the invention. The dummy receptacle is attached to the cord at a point in close proximity to the plug base. 
         FIG. 7   b  shows a schematic of the plug and the dummy receptacle of  FIG. 7   a  with the plug plugged into the dummy receptacle. 
         FIG. 7   c  shows a schematic of a plug and a dummy receptacle configured according to still another embodiment of the invention. The dummy receptacle is attached to the plug by means that includes a sleeve. 
         FIG. 7   d  shows a schematic of the plug and the dummy receptacle of  FIG. 7   c  with the sleeve shown in section. 
         FIG. 7   e  shows a schematic of a plug and dummy receptacle configured according to yet another embodiment of the invention. 
         FIG. 8   a  shows a schematic of a perspective view of a two piece three prong plug, comprising a plug base and a prong assembly, configured according to a further embodiment of the invention. 
         FIG. 8   b  shows a schematic of an orthogonal end view of the plug base shown in  FIG. 8   a.    
         FIG. 8   c  shows a schematic of an orthogonal side view, shown in partial section, of the plug base shown in  FIG. 8   a.    
         FIG. 8   d  shows a schematic of an orthogonal side view of the prong assembly shown in  FIG. 8   a.    
         FIG. 8   e  shows a schematic of an orthogonal side view, shown in section, of the prong assembly shown in  FIG. 8   a.    
         FIG. 9   a  shows a schematic of a perspective view of a two piece three prong plug, comprising a plug base and a prong assembly, configured according to a yet further embodiment of the invention. 
         FIG. 9   b  shows a schematic of a perspective view of a two piece three prong plug, comprising a plug base and a prong assembly, configured according to a still further embodiment of the invention. 
         FIG. 9   c  shows a schematic of an orthogonal side view of the two piece plug shown in  FIG. 9   a.    
         FIG. 9   d  shows a schematic of an orthogonal side view, in section, of the prong assembly shown in  FIG. 9   a.    
         FIG. 9   e  shows a schematic of an orthogonal side view, in partial section, of the two piece plug in  FIG. 9   a  with the two pieces attached to each other. 
         FIG. 9   f  shows a schematic of an orthogonal side view, in section, of the prong assembly shown in  FIG. 9   b.    
         FIG. 10  shows a schematic of a plug with individually removable prongs configured according to another embodiment of the invention. 
         FIG. 11  shows a schematic of a replacement plug comprising a brace element configured according to a further embodiment of the invention. 
         FIG. 12   a  shows a schematic of the orthogonal view of a plug configured according to yet another embodiment of the invention. The brace element (in fully retracted position) and plug base are shown in section and partial section respectively. 
         FIG. 12   b  shows a schematic of the plug in  FIG. 12   a  with the brace element in deployed position. 
         FIG. 12   c  shows an orthogonal end view schematic of the brace element shown in  FIGS. 12   a  and  12   b.    
         FIG. 12   d  shows a sectioned orthogonal side view of the brace element shown in  FIGS. 12   a  and  12   b.    
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
       FIG. 1  shows a schematic of a three prong plug  1 , configured according to an embodiment of the invention, comprising plug base  2 , prongs  3 ,  4 , and  5 , electrical cord  6 , and integral brace element  7 . Brace element  7  is slidably attached to and integral with plug base  2 . Plug  1  may be attached, for example, to one end of a power cord, such as an extension cord or the electric cable of a tool or appliance. Electrically conductive prongs  3 ,  4  and  5  are connected to three mutually insulated conductors (not shown) within an insulated electric cord or cable  6 . The plug base  2  encapsulates the connections between prongs  3 ,  4 , and  5  and the corresponding conductors in the electrical cord  6 . Plug base  2  may be fabricated, for example, from a plastic material by injection molding. A plastic plug base may be produced by, for example, using an overmolding or insert molding process. In the case, for example, of a typical NEMA 5-15 plug, prongs  3 ,  4 , and  5  would connect to the hot, neutral and ground terminals respectively when plugged into a matching electrical receptacle. NEMA5-15 is a designation of a plug configuration promulgated by the National Electrical Manufacturers Association (NEMA). This NEMA standard specifies the standard size and placement of prongs for 15 ampere three prong plugs commonly used in the United States. Brace element  7  is shown in its retracted position in  FIG. 1 . It is preferred that plug  1  in  FIG. 1  be configured such that, when the brace element is retracted, there is a substantially smooth transition between the outer envelope of plug base  2  and the outer envelope of the brace element  7 . This will reduce possible interference among multiple plugs that are plugged into adjacent receptacles, and also help reduce the concentration of externally induced stresses in the brace element, for example, when the plug is exposed to crushing forces. 
       FIG. 2   a  shows a schematic of the three prong plug  1  of  FIG. 1  with the brace element  7  in a deployed position shielding substantially the entire length of prongs  3 ,  4  and  5  and bracing them against each other. Plug base  2  has an exposed segment  8  that is uncovered by the deployment of the brace element  7 . The exposed segment  8  of plug base  2  is hidden by the brace element  7  when it is fully retracted. 
     The exemplary embodiment of the brace element shown in  FIG. 1  and  FIG. 2   a  is configured to operate with two flat blade prongs and a third prong that has the shape, substantially, of a circular cylinder. However, a brace element may be configured to accommodate any number of prongs of various shapes and sizes. 
       FIG. 2   b  shows a schematic of an end view of the brace element  7  of  FIG. 1  and  FIG. 2   a  with the three openings configured to closely and slidably receive prongs  3 ,  4 , and  5  shown in  FIG. 1  and  FIG. 2   a .  FIG. 2   c  shows a sectioned side view of brace element  7  which comprises a substantially cylindrical section  9  with a stop  10  at one end, and a web-plate  11  at the other. The web-plate  11  is configured with holes that allow the plate to slide along and be guided by the prongs. The web-plate supports the prongs and braces them against each other. The cylindrical section  9  and radially inwardly protruding ridge  10   a  also assist in guiding the motion of the brace element  7 . The stop  10  limits the motion of the brace element so that it does not slip off the end of the prongs when deployed. The brace element can be made of one or more conducting and non-conducting materials such as, for example, plastics, ceramics and metals. Materials of high strength are preferred so long as the use of conductive materials does not interfere with the proper and safe operation of the plug, such as, for example, by electrically shorting a line voltage prong with a ground prong or exposing users to electrical shock. 
       FIG. 3   a  shows a schematic of a three prong plug  12 , configured according to another embodiment of the invention, comprising plug base  13 , prongs  14 ,  15 , and  16 , electrical cord  17 , and brace element  18 . Brace element  18  is slidably attached to and integral with plug base  13 .  FIG. 3   b  shows a schematic of the three prong plug  12  of  FIG. 3   a  with the sliding brace element  18  deployed to a position near the distal end of the prongs and bracing them against each other. Tether  19  limits the motion of the brace element and does not allow the brace element to slip off the prongs.  FIG. 3   c  shows a schematic of an orthogonal end view of the brace element  18  of  FIG. 3   a  and  FIG. 3   b .  FIG. 3   d  shows a sectioned view of brace element  18  which comprises web-plate  20 , tether  19  and stop  21  which keep the brace element  18  from slipping off the prongs. 
       FIG. 3   e  is a schematic showing a perspective view of a plug  22 , with plug base  23  and brace element  24 . Brace element  24  is integral with and slidably attached to the plug base  23 . Brace element  24  comprises a protrusion  25  which is slideably received by channel  26  located along prong  27 . Channel  26  extends along part of the length of prong  27 . Any of the prongs may be configured to receive a protrusion attached to the brace element such that its motion is constrained. 
       FIG. 3   f  shows the plug  22  of  FIG. 3   e  with the brace element  24  in a fully deployed position, where the protrusion  25  (not shown) has reached the distal end of channel  26 . 
     The protrusion in  FIG. 3   e  is preferably flexible so that it can be snapped into the channel during assembly. 
     Alternatively,  FIG. 3   g  shows a plug  28  comprising brace element  24   a  and screw  29 . The distal end of screw  29  is slidably engaged in channel  26 . The extent to which the brace element  24   a  may be deployed is limited when the tip of screw  29  reaches the distal end of channel  26 .  FIG. 3   h  shows that the tip of screw  29  penetrates the opening in brace element  24   a  which receives prong  27  shown in  FIG. 3   g.    
       FIG. 4   a  shows a schematic of a plug adapter  30 , configured according to still another embodiment of the invention, comprising adapter base  31 , brace element  32  and prongs  33 ,  34  and  35 . Brace element  32  is slidably attached to and integral with adapter base  31 . The brace element is shown in a fully retracted position. Also shown is a schematic of a conventional plug  36 , plug base  37 , prongs  38 ,  39 , and  40 , and cord  41 . Not shown are receiving terminals of the plug adapter  30  which are configured to receive prongs  38 ,  39  and  40 . When conventional plug  36  is plugged into plug adapter  30 , prongs  33 ,  34 , and  35  are electrically connected to prongs  38 ,  39  and  40  respectively. Brace element  32  may be deployed to shield and buttress prongs  33 - 35 . The plug adapter prongs are configured to be received in a conventional receptacle designed to receive the prongs of conventional plug  36 . 
       FIG. 4   b  shows a schematic of the conventional plug  36  and plug adapter  30  of  FIG. 4   a , wherein the brace element  32  has been deployed. Exposed portion  42  of the adapter base  31  is hidden by the cylindrical portion of brace element  32  when it is fully retracted. With the sliding brace element deployed, prongs  33 ,  34  and  35  are shielded and the space between the prongs is filled, by a portion of the web-plate, such that the prongs are also braced against lateral deforming or crushing forces. The brace element is slidably attached to the adapter base. The exemplary embodiment of the brace element shown in  FIGS. 4   a  and  4   b  is configured to operate with two flat blade shaped prongs and a prong that is shaped substantially as a circular cylinder. However, the brace element may be configured to operate with any number of prongs or prongs of any shape and size. 
       FIG. 5   a  shows a schematic of a three prong plug  55  configured according to a further embodiment of the invention. Conductors (not shown) in electrical cord  56  are electrically connected to prongs  57  and  58  and to a third prong which is not shown. The plug base  59  is typically fabricated substantially from an insulating material such as an injection molded plastic. In  FIG. 5   a , brace element  60  is shown in a fully retracted position and in section.  FIG. 5   b  shows a schematic of the plug in  FIG. 5   a  with the brace element  60 , comprising cylindrical section  62  and web-plate  61 , in a fully deployed position. In the deployed position, the terminals are shielded and also supported near their tips by the web-plate  61  of the brace element  60 . Brace element  60  is slidably attached to an integral with plug base  59 . 
     Shield  60   a , a schematic of which is shown in  FIG. 5   c , may be configured with a cylindrical piece  62   a  that is substantially open at both ends. In such a configuration, the deployed shield  60   a  protects the prongs but would not contact or support the prongs directly. A brace element may be fabricated as a single piece or as an assembly of multiple pieces.  FIG. 5   d  shows a brace element  60   b  which comprises a substantially cylindrical piece  62   b  and a web-plate  61   b . The cylindrical piece may be constructed from, for example, a metal such as steel, while web-plate  61   b  may be fabricated from, for example, a plastic material. 
     The schematic in  FIG. 5   e  shows a three prong plug  63 , comprising a plug base  64  and a brace element  65 , configured according to a still further embodiment of the invention. Brace element  65  is slidably attached to and integral with plug base  64 . The brace element and plug base are shown in section and partial section respectively. Conductors (not shown) in electrical cord  66  are electrically connected to prongs  67  and  68  and to a third prong which is also not shown. In  FIG. 5   e , the brace element  65 , which is in a fully retracted position, comprises a web-plate  69 , a tether  70 , and a stop  71 .  FIG. 5   f  shows a schematic of the plug in  FIG. 5   e  with the brace element  65  in a fully deployed position. In this position, each of the prongs is supported both at its base end as well as being buttressed near its tip by the web-plate  69 . The cavity  72  in plug base  64  is configured to accept tether  70  and stop  71 . The opening  73  of the cavity and stop  71  are configured such that the stop  71  may be forced into the cavity during assembly of the plug, but once inside be securely retained therein. The tether  70  and stop  71  of the brace element work in conjunction with the cavity opening  73  to stop the brace element from being deployed beyond the end of the prongs. The tether is preferably sufficiently rigid so that the brace element may be retracted by pushing the web-plate towards the plug base. 
       FIG. 6   a  is a schematic of a plug adapter  77  configured according to a further embodiment of the invention. Conventional plug  76  is coupled with and attached to a plug adapter  77 . The brace element  78  and plug adapter base  79  are shown in section and partial section respectively. Brace element  78  is slidably attached to adapter base  79 . The prongs  80  and  81  of the plug  76  are received in terminals  80   a  and  81   a  which are electrically connected to prongs  82  and  83  respectively, of the plug adapter  77 . 
       FIG. 6   b  shows the plug and plug adapter of  FIG. 6   a  with the brace element in a fully deployed position. In  FIG. 6   b , a set screw  84  is used to bind the plug adapter base  79  to plug  76 . It is preferred that plug adapter  77  in  FIG. 6   a  be configured such that there is a substantially smooth transition between the outer dimensions of plug base  76  and the outer dimensions of brace element  78  when it is fully retracted. This will reduce possible interference among multiple plugs that are plugged into adjacent receptacles and help avoid points of stress concentration in the brace element when the plug is, for example, stepped on or otherwise exposed to crushing forces. 
       FIG. 7   a  shows a schematic of yet another embodiment configured according to the invention. A dummy receptacle  86 , a brace element that is not an integral part of the plug base  85   a , is configured so it may be attached to the end of the power cord  88  in close proximity to the plug base by means of strap  87 . Strap  87  is preferably made of an elastic material. 
       FIG. 7   b  shows the plug  85  of  FIG. 7   a  plugged into the dummy receptacle  86 , wherein the prongs of the plug are braced and protected from crushing forces. The band  87  is configured so that the dummy receptacle will not interfere with the normal use of the plug with conventional outlets, receptacles or power strips, especially where several receptacles are used in close proximity to each other. Preferably the dummy receptacle is configured so that the prongs of the plug fit snugly into the receptacle holes so that the prongs are supported against crushing transverse forces along their entire lengths. 
       FIG. 7   c  shows a schematic of still another embodiment according to the invention wherein dummy receptacle  89  is configured so that it may be attached to plug base  90  located at the end of an electric cord  91 . Sleeve  92  and strap  93  are used to flexibly attach the dummy receptacle  89  to plug base  90 .  FIG. 7   d  is a schematic showing the plug and dummy receptacle of  FIG. 7   c  where sleeve  92  is in section. It is preferred that sleeve  92  be made of a stretchable material so that opening  93  of the sleeve may be stretched sufficiently to allow plug base  90  to pass through. The sleeve may be bound to the plug base  90  by stretching it over the plug base and then releasing it so that the plug base may be securely gripped by the sleeve. Alternatively, the dummy receptacle may be attached to an electric cord or a plug by using, for example, screws, bolts, adhesives, Velcro straps, or collars. 
       FIG. 7   e  shows a schematic of yet another embodiment configured according to the invention wherein the prongs of conventional plug  94  are plugged into and supported, braced and shielded by brace element  94   a . The brace element  94   a  is flexibly attached to cord  94   b  by collar  94   c  and lanyard  94   d . The collar  94   c  may be a split collar that is configured to slide freely along the cord  94   b.    
       FIG. 8   a  shows a schematic of a two piece electric plug  95  configured according to a further embodiment of the invention which comprises a plug base  96  and a removable prong assembly  97 . If damaged, the prong assembly, which comprises three prongs  98   a ,  98   b  and  98   c , may be readily separated from the plug base and replaced. Plug base  96  also comprises three receiving terminals  99   a ,  99   b  and  99   c , each of which is electrically connected to a separate conductor (not shown) in cord  100 . These connections are preferably encapsulated in a plastic material by injection molding. Alternatively, the plug base may be constructed in one or more pieces wherein the connections are encased in one or more materials, such as for example, plastics, ceramics, bakelite, or various metals. Each of the receiving terminals  99   a ,  99   b  and  99   c  of the plug base is configured and positioned to receive one of the corresponding protruding electrical contacts or terminals  101   a ,  101   b , or  101   c  of the prong assembly  97  when the constituent pieces of the plug are assembled. Each of contacts or terminals  101   a ,  101   b  and  101   c  is electrically conductively connected to prongs  98   a ,  98   b  or  98   c  respectively. It is preferred that the prong assembly be fabricated using injection molding. A fastening screw (not shown) may be used to secure prong assembly  97  to plug base  96 . Hole  101  and threaded hole  102  are configured to receive such a fastening screw. It is preferred that, when assembled, the two piece plug  95  be no larger than a conventional plug. 
       FIG. 8   b  and  FIG. 8   c  show orthogonal schematic views of the plug base of the two piece plug  95  shown in perspective in  FIG. 8   a .  FIG. 8   c , in partial section, shows receiving terminals  99   a  and  99   c  and threaded hole  102 .  FIG. 8   d  shows an orthogonal schematic side view of the prong assembly  97  and a portion of screw  103  for attaching prong assembly  97  to plug base  96 .  FIG. 8   e  shows an orthogonal schematic sectioned side view of the prong assembly  97 . Each of the prongs and contacts of the prong assembly shown in  FIG. 8   e  may be made as multiple pieces that are electrically connected, such as prong  98   a  and contact  101   a  or as single piece conductors, such as prong  98   c  and contact  101   c . The electrical contacts  101   a ,  101   b , or  101   c  may be of any convenient size, shape, orientation or position that can be received by corresponding receiving terminals  99   a ,  99   b  and  99   c  of the plug base. Fastening screw  103  may be used to secure the prong assembly  97  to the plug base  96 . 
       FIG. 9   a  shows a schematic of a two piece plug  110  configured according to a still further embodiment of the invention. Two piece electric plug  110  comprises a plug base  111  and removable prong assembly  112 . The removable prong assembly, which comprises three prongs  113   a ,  113   b  and  113   c  may be readily removed, discarded and replaced if damaged. Plug base  111  comprises three terminals  114   a ,  114   b  and  114   c  each of which is electrically connected to a conductor (not shown) in cord  115 . These connections are preferably encapsulated in a plastic material by injection molding. Alternatively, the plug base may be constructed in one or more pieces such that the connections are encased in one or more materials, such as, for example, plastics, ceramics, bakelite, or various metals. Each of the three terminals  114   a ,  114   b  and  114   c  is configured and positioned to electrically connect to a corresponding electrical contact (not shown) on the prong assembly. Each such contact of the prong assembly is electrically conductively connected to one of the prongs  113   a ,  113   b  and  113   c . A fastening screw (not shown) may be used to secure prong assembly  112  to plug base  111 . Hole  116  and threaded hole  117  are configured to receive such a fastening screw. 
     The electrical terminals  114   a ,  114   b  and  114   c  shown in  FIG. 9   a  are protruding terminals. The corresponding contacts on the prong assembly would preferably be receiving terminals.  FIG. 9   b  shows a schematic of a two piece plug  118  wherein the plug base  119  comprises two protruding electrical terminals  120   a  and  120   b  and one receiving terminal  120   c . The prong assembly  121  comprises one protruding terminal  122  and two receiving terminals (not shown), and prongs  123   a ,  123   b  and  123   c.    
       FIG. 9   c  shows an orthogonal schematic view of the two piece plug  110 , shown in perspective in  FIG. 9   a , comprising plug base  111  and prong assembly  112 . Also shown are two protruding terminals,  114   a  and  114   c , of plug base  111 .  FIG. 9   d  shows a sectioned view of the prong assembly  112 , which comprises receiving terminals  124   a  and  124   c  electrically connected to prongs  113   a  and  113   c  respectively. The third receiving terminal of prong assembly  112  is not shown in  FIG. 9   d.    
     The plug base  111  is preferably manufactured from plastic by injection molding. Base  111  is attached to an electric cord  115  which comprises three electrical conductors (not shown). Each of the three electrical contacts  114   a ,  114   b  and  114   c , is electrically conductively connected to a corresponding electrical conductor in the cord  115 . 
       FIG. 9   e  shows an orthogonal side view of the assembled two piece plug  110  of  FIG. 9   a , comprising plug base  111  and prong assembly  112 . Prongs  113   a ,  113   b  (not shown) and  113   c  are electrically connected to terminals  114   a ,  114   b  (not shown) and  114   c  of the plug base respectively. The prongs  113   a ,  113   b  (not shown) and  113   c  in the plug  110  as assembled are electrically conductively connected to conductors (not shown) in cord  115 . If the prongs of plug  110  are damaged, prong assembly may be readily replaced. 
     It is preferred that the two piece electric plug  111  be substantially no larger in size than a conventional injection molded plug. For example, it is preferred that a NEMA5-15 two piece electric plug, such as shown in  FIG. 9   e , be no larger than approximately 1.25 inches in diameter (Dimension D) and have an overall length of no more than 1.5 inches (Dimension L). 
       FIG. 9   f  shows a schematic side view (in section) of prong assembly  121  shown in  FIG. 9   b . Prong assembly  121  comprises prongs  123   a  and  123   c  which are electrically connected to receiving terminal  122   a  and protruding terminal  122   c . For safety, it is preferred that terminals of the prong assembly, that in use may achieve elevated voltage, for example, in excess of 12 volts AC or DC, be receiving terminals. It is further preferred that prong assembly terminal that in use is a ground terminal be protruding so as to help to align and secure the prong assembly to the plug base. 
       FIG. 10   a  shows yet a further embodiment configured according to the invention. Electrical plug base  140  is configured with threaded holes  141  and  142 . Prongs  146  and  147  are individually removably attached to the plug base  140  by means of threaded holes  141  and  142 . End views of three threaded holes  141 ,  142  and  143  of the plug are shown in  FIG. 10   b . The flat prong  147  in  FIG. 10   c  has alignment or positioning tabs  150  that snap in place in recesses  151 . The prong  146  in  FIG. 10   c , which is substantially a circular cylinder, has a flange  153  that fits in recess  154 . With this configuration, the prongs can be replaced readily if they are bent or damaged. It is preferred that the plug base  140  be fabricated by injection molding. 
       FIG. 11  shows a schematic of a three prong replacement plug  160  configured according to still a further embodiment of the invention comprising plug base  161  and brace element  162 . Plug  160  is configured to accept a three conductor cord  163  such that prongs  164   a ,  164   b  and  164   c  may be electrically conductively connected to conductors  165   a ,  165   b  and  165   c  respectively. 
       FIG. 12   a  shows a schematic of a three prong (two of which are shown) plug configured according to yet another embodiment of the invention. Plug  110  comprises plug base  171 , cord  172 , ground prong  173 , line voltage prong  174 , neutral prong (not shown), and retracted brace element  175 . It is configured so that the brace element may be deployed automatically. The brace element  175  comprises stop  176 , actuator  177 , which is preferably rigid, and protruding boss  178 . The actuator has an insert  179  at its tip which is fabricated from a ferrous or ferromagnetic material or other materials that are attracted by a magnet. 
     The plug base  171  comprises a cavity  181  that is configured to receive actuator  177  and a cavity for receiving protruding boss  178 . Cavity  181  also comprises a spring  182  which is compressed by the actuator  177  when the brace element is in a retracted position. The protruding boss  178  is configured to increase the rigidity of the portion of the web-plate that is interposed in between the prongs. 
     The plug base  171  also comprises an electromagnet  183  that may be energized by coil  184 . Coil  184  is connected to line voltage prong  174  by means of contact  185  and a neutral prong (contact for neutral prong not shown). The coil  184  is configured to draw a small fraction of the rated power of the plug when the prongs are engaged in a powered receptacle. When so energized, the current flowing through the coil causes the electromagnet  183  to become magnetized and attract insert  179  with sufficient force to overcome the force exerted by compressed spring  182  on the actuator. When the plug  170  is withdrawn from the receptacle, the current in coil  184  is interrupted and the magnetism of electromagnet  183  collapses allowing spring  182  to automatically deploy the brace element by forcing actuator  177  to move outwardly in cavity  181 . It is preferred that the current draw of coil  184  be no greater than 1% of the rated current draw of the plug and more preferably no greater than 0.1% of the rated current draw of the plug.  FIG. 12   b  shows plug  170  with brace element  175  in a fully deployed position. Spring  172  is extended. The outward motion of the brace element is interrupted when the stop  176  reaches radially outwardly protruding rim  186 . Cavity  181   a  receives boss  178  when the brace element is retracted. 
       FIG. 12   c  shows the bottom orthogonal view of brace element  175  shown in  FIGS. 12   a  and  12   b . Openings  189  and  190  are sized to slidably receive prongs  173  and  174  shown in  FIGS. 12   a  and  12   b . Opening  190   a  is sized to slidably receive neutral prong (not shown). 
       FIG. 12   d  shows a side view sectioned schematic of the brace element  175  shown in  FIGS. 12   a ,  12   b  and  12   c . The brace element comprises actuator  177  and cylindrical section  191 . The cylindrical section  191  connects stop  176  to web-plate  192 . Actuator  177  is configured with insert  179  at its distal end. The portion of the web-plate located in between the prongs is augmented by protruding boss  178 . 
     Several embodiments have been described herein, some with reference to accompanying figures. These are intended to be illustrative. The following claims are not limited to or by the described illustrative embodiments, figures, stated objects of the invention or the abstract. Furthermore, various presently unforeseen or unanticipated combinations of the disclosed embodiments, or their elements, or alternatives, variations or improvements which may become apparent to those of ordinary skill in the art are also intended to be encompassed by the following claims.