Abstract:
The present invention relates to a power connector for receiving an electric plug. The power connector is provided with a three-piece safety shutter architecture to prevent unwanted or improper insertion of a single plug pole into the power receptacles. In this architecture, the locking bar is formed with a first and a second tabs. The first and second tabs work with a protrusion formed therebetween to engage with the safety shutters and keep the safety shutters spaced apart from each other by a predetermined distance, so that the safety shutters are slidably latched in parallel by the locking bar and only allowed to travel dependently of each other along the travel direction, making the invention to meet the strict international safety standards for household plugs, adapters and socket-outlets.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of U.S. application Ser. No. 14/683,248 filed Apr. 10, 2015, the entirety of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a power connector for receiving an electric plug, and more particularly to a power connector provided with an improved safety shutter, allowing the invention to meet the strict international safety standards for household plugs, adapters and socket-outlets. 
     Description of Related Art 
     Many European countries, including Portugal, Finland, Denmark, Norway and Sweden, require installment of safety shutters in socket outlets to prevent children from poking objects into them. To meet the requirement that the socket shutters can be opened up only when the live and neutral poles of a plug are inserted at the same time, some single-piece shutter designs have been proposed in the art, such as those disclosed in Great Britain Patent Publication Nos. 793000 and 2199996. However, such designs were frequently found hard to operate, as considerable force was needed to drive the relatively large shutter plate to its open position. It has also been found that the safety shutters of some conventional sockets will fail to work and the receiving surfaces of the safety shutters can wear out quickly, when receiving an electric plug with relatively sharp edges, such as a typical US polarized plug  9  having an edge inclined at 50° relative to its flat tip as shown in  FIG. 6 . The shortcomings are likely due to the small contact area between the plug tips and the safety shutters, as well as the relatively weak component force produced in the direction perpendicular to the insertion direction. 
     Additional problems may arise due to the limited space which the shutter plate must share with other elements in the socket cavity. For example, referring to the traditional universal socket arrangement illustrated in  FIG. 14 , an upright grounding system  50 ″″ is disposed at the center of the socket cavity and, thus, the shutter plate  30 ″″ is spatially hindered from moving towards the grounding system  50 ″″. To address this issue, the shutter plate  30 ″″ was arranged to open up the outlets by moving away from the grounding system  50 ″″. As a consequence, the traditional device is unsatisfactorily large in size and the portability thereof is undesirably compromised. Moreover, when a socket of this type receives a Schuko CEE 7/4 plug having flat grounding contacts, the safety shutters  30 ″″, biased by the spiral springs  33 ″″, apply a force to the live and neutral poles of the Schuko plug and, therefore, tend to push the plug away from the grounding metal of the socket to create a gap between the plug and the socket, causing a poor grounding connection. An unofficial test conducted by the inventors showed that the conventional safety shutters could disadvantageously lead to unreliable grounding connection at a defect rate as high as 40%. 
     The co-pending U.S. application Ser. No. 14/683,248, assigned to the present applicant, discloses a power connector provided with a three-piece safety shutter architecture. In this architecture, a pair of safety shutters are interlocked with each other by slidably engaging the guide members of the safety shutters with the tabs extending from a traversely movable locking bar, where one of the guide members is in the form of a guide groove and the other is in the form of a side wall of the safety shutters. While the three-piece safety shutter architecture was proved to overcome the disadvantages above to a great extent, there remains a need for an improved power connector device that can fulfill the national safety requirements, especially when receiving a Schuko plug that is normally designed to be insertable in either way. 
     SUMMARY OF THE INVENTION 
     In one aspect provided herein is a new and improved power connector for engagement with an electric plug, which is equipped with safety shutters for preventing unwanted or improper insertion of a single male contact of the plug into the power receptacles thereof. The power connector comprises:
         a dielectric housing, comprising a top face panel, wherein the top face panel is formed with two power receptacles through which the male power contacts may be inserted;   two power output frames mounted spaced apart in the housing, each having an output contact portion facing towards the top face panel and adapted for receiving the respective male contact of the electric plug through the respective power receptacle along an insertion direction, and an input portion remote from the top face panel;   a pair of safety shutters mounted in parallel within the housing, wherein the safety shutters are biased in a travel direction generally perpendicular to the insertion direction by respective biasing members to an advancing position to close the power receptacles and each formed with a guide groove; and   an elongated locking bar mounted in the housing in a manner extending and movable along a traverse direction traversing the travel direction and unmovable in the travel direction, wherein the locking bar is provided with a first tab and a second tab which are separate from each other by a given distance and slidably engage the respective guide grooves, so that the two guide grooves are spaced apart in parallel by said given distance;   whereby the safety shutters travel dependently of each other along the travel direction to a retracted position to open the power receptacles in response to insertion of the male power contacts.       

     By virtue of the three-piece safety shutter architecture described above, the problems caused by the conventional one-piece shutter plate are solved. In short, the safety shutters are slidably latched in parallel by the locking bar and only allowed to travel dependently of each other along the travel direction, so that the locking bar can stop a single power pin to open the live receptacle, but will slide along the traverse direction to open the safety shutters when the safety shutters are pushed by two power pins at the same time. In comparison to the counterpart device shown in  FIG. 13  which meets the U.S. national Standards and is not equipped with safety shutters, the power connector disclosed herein can prevent unwanted or improper insertion of a single plug pole into the power receptacles. It is also important to note that the universal socket arrangement disclosed herein is so compact that it can reduce the overall size of the power connector by half as compared to the traditional device shown in  FIG. 14 . 
     In a preferred aspect provided herein, the locking bar is further formed with a protrusion between the first tab and the second tab, and the protrusion is formed with two end faces facing towards and adapted to slidably abut against the respective side walls of the safety shutters. As such, the first tab, the second tab and the protrusion work together to keep the safety shutters spaced apart from each other by a predetermined distance, thereby making the safety shutters travel dependently of each other. 
     In another preferred aspect provided herein, the safety shutters each includes a slant surface arranged proximate to the top face panel and adapted for receiving a pressing force from the male power contact. More preferably, the slant surfaces are configured to incline at an angle of about 30 degree relative to the travel direction, thereby overcoming the problems regarding the failure of safety shutters. 
     In another preferred aspect provided herein, the power connector is further provided with a common grounding frame, which comprises a resilient metal clip facing towards the top face panel. The resilient metal clip has two free ends extending upwardly and outwardly beyond the top face panel to constitute a Schuko contact in the form of two metal plates anchored on the top face panel. More preferably, the Schuko contact is bent over to provide additional strength for countering the downward force generated by insertion of a three-pin plug. 
     In yet another preferred aspect provided herein, the safety shutters are so arranged that they are driven to move towards the Schuko contact in response to insertion of the electric plug. It was unexpectedly found by the inventors that such arrangement facilitates the attachment of the flat ground contact of a Schuko CEE 7/4 plug onto the Schuko contact of the power connector disclosed herein by urging the safety shutters to push the plug towards the Schuko contact. As a result, the potential gap between the plug and the power connector is almost non-existent, and the problem of unreliable grounding connection occurring in the traditional devices is reduced to the minimum. 
     In still another preferred aspect provided herein, the power output frames each comprises an input portion facing towards the bottom face panel, and the common grounding frame comprises a common grounding base facing towards the bottom face panel. The input portions and the common grounding base are each directly riveted with a conductive coupler for electrical connection to an external power source. 
     The power connector disclosed herein is intended to serve as a common architecture applicable to various forms of adapters and socket-outlets. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is an exploded schematic view of a power connector according to an embodiment of the invention; 
         FIG. 1B  is a perspective schematic view of a power connector according to an embodiment of the invention; 
         FIG. 2  shows the top face panel of a power connector according to an embodiment of the invention; 
         FIG. 3  shows the power output frame of a power connector according to an embodiment of the invention; 
         FIGS. 4A-4D  are schematic views of the safety shutters according to an embodiment of the invention; 
         FIGS. 5A-5D  are schematic views showing the operation of the safety shutters according to an embodiment of the invention; 
         FIG. 6  is a schematic diagram showing that a US polarized plug is brought in contact with the safety shutters; 
         FIGS. 7A-7B  are schematic views of the common grounding frame according to an embodiment of the invention; 
         FIG. 7C  is a schematic view of the common grounding frame according to an alternative embodiment of the invention; 
         FIGS. 7D and 7E  are schematic views of power connectors according to one embodiment of the invention, in which the common grounding frame is free of a Schuko contact; 
         FIG. 8A  is a schematic view of the power connector according to one embodiment of the invention, which is in the form of a universal socket; 
         FIG. 8B  is a schematic diagram showing the wire holder of the universal socket according to one embodiment of the invention; 
         FIG. 9  is a schematic view of the power connector according to an alternative embodiment of the invention, which is in the form of a universal power strip; 
         FIG. 10A  is a schematic view of the power connector according to another alternative embodiment of the invention, which is in the form of a universal adapter; 
         FIG. 10B  is a schematic diagram showing the direct wiring connection between the common grounding frame and the ground pin; 
         FIG. 10C  is a schematic diagram showing the direct wiring connection between the power output frame and the power pin; 
         FIGS. 11A-11B  are perspective views of the power connector according to another alternative embodiment of the invention, which is in the form of an all-in-one adapter kit; 
         FIG. 12  is a schematic diagram showing that the all-in-one adapter kit are assembled to constitute a pyramid-like packaging; 
         FIG. 13  is a schematic view of a power connector which is not equipped with safety shutters; and 
         FIG. 14  is an exploded schematic view of a power connector known in the art. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The technical contents and characteristics of the present invention will be apparent with reference to the detailed description of preferred embodiments accompanied with related drawings as follows. 
     A power connector  1  according to a preferred embodiment of the invention is shown in  FIGS. 1A and 1B , which comprises a dielectric housing  10 , two power output frames  21 ,  22  mounted in the housing  10 , a pair of safety shutters  31 ,  32  mounted in parallel within the housing  10 , and an elongated locking bar  40  detachably and slidably engaged with both safety shutters  31 ,  32 . 
     The dielectric housing  10  comprises a top face panel  11 , a bottom face panel  12  and a surrounding side wall to define an interior cavity  13 . Desirably, the dielectric housing  10  includes two partition walls arranged in parallel to divide the interior cavity  13  into a middle chamber disposed between the partition walls and two lateral chambers disposed at two opposite sides of the middle chamber. The dielectric housing  10  is made of any dielectric material known in the art, such as plastics and phenolic resins. In a preferred embodiment, the top face panel  11  and the rest of the housing  10  are separately injection molded and then assembled together to form a single module. 
     The top face panel  11  is formed with a plurality of receptacles to constitute a universal socket layout for receiving the plug types in common use around the world, which include but are not limited to European, British, US, North African and Australian plugs. As shown in  FIG. 2 , the universal socket layout includes two power receptacles, i.e., the neutral (N) and live (L) receptacles  111 ,  112 , adapted to receive the neutral and live contacts of an electric plug. Preferably, one or more grounding receptacles are formed on the top face panel  11  to receive the grounding contact of the plug, which may include and is not limited to a Schuko grounding receptacle  113 , a Swiss grounding receptacle  114  and an Italian grounding receptacle  115  merged with a Brazil grounding receptacle  116 . It should be noted that the Swiss grounding receptacle  114  disclosed herein is located at very outside of the universal socket layout, in contrast to its conventional location right next to the Italian grounding receptacle  115 . The new location will force a Swiss plug to be inserted into the power connector  1  in a different orientation and thus overcome the N-L reversal problem as in the traditional universal socket layout, a problem having been lasting for the past twenty five years. 
     The power output frames  21 ,  22  are secured inside the housing  10  in a manner spaced apart from each other, and preferably held within the lateral chambers of the interior cavity  13 , respectively. Each of them is preferably a single-piece element made of material with high electrical conductivity, preferably made of one or more conductive metal elements or metal alloys, such as brass or phosphor copper. The power output frames  21 ,  22  can be fabricated by any process known in the art, including metal stamping and punch pressing. As shown in  FIGS. 1A and 3 , the power output frames  21 ,  22  each includes an output contact portion  211 ,  221  facing towards the top face panel  11  and an input portion  212 ,  222  remote from the top face panel  11 , preferably facing towards the bottom face panel  12 . The output contact portion  211 ,  221  each includes a resilient member for holding the male power contacts of a plug, which is preferably configured in the form of a resilient metal clip having a gripping part conforming in shape to the shapes of the prong-, blade- and pin-shaped male contacts of the plugs used in various countries. The output contact portion  211 ,  221  are registered with the power receptacles  111 ,  112 , so that they are adapted for receiving the power contacts of the electric plug through the power receptacles  111 ,  112  along an insertion direction indicated by the arrow A, thereby establishing electrical connection between the power output frames  21 ,  22  and the electric plug. 
     Now referring to  FIGS. 4A-4B , the safety shutters  31 ,  32 , preferably made of dielectric material, are mounted within the housing  10  and maintained in generally parallel spaced relationship with each other by the locking bar  40  as described below. This can be realized by defining two confined parallel paths in the housing  10  for the safety shutter  31 ,  32  to travel back and forth. In the preferred embodiments, the travel paths are defined by a pair of support members  34 ,  35  alone or together with the housing  10 . The support members  34 ,  35 , preferably made of dielectric material, are mounted in the two lateral chambers of the interior cavity  13 , each comprising two opposite side walls  341 ,  342 ,  351 ,  352  and a travel path  343 ,  353  extending between the opposite side walls  341 ,  342 ,  351 ,  352 , along which the safety shutters  31 ,  32  may slide between the two opposite side walls  341 ,  342 ,  351 ,  352  in a travel direction indicated by the arrow B generally perpendicular to the insertion direction A and generally parallel to the top face panel  11 . 
     The safety shutters  31 ,  32  are each attached at the rear end thereof to a biasing member  33  which is in turn anchored to the rear walls  342 ,  352 . Desirably, the rear ends of the safety shutters  31 ,  32  and the walls  342 ,  352  are each provided with a stud  324 ,  354  for anchorage of the biasing members  33 . In the preferred embodiments, the biasing member  33  is a slightly compressed spring extending in the direction B, so that the front ends of safety shutters  31 ,  32  are normally urged to abut against the front walls  341 ,  351  and biased to their advancing position as shown in  FIG. 4B , thereby closing the power receptacles  111 ,  112 . It is apparent to those skilled in the art that other types of biasing members can also be used in the invention, as long as they are useful in biasing the safety shutters  31 ,  32  to the advancing position. 
     As shown in  FIGS. 4C-4D , the safety shutters  31 ,  32  are each provided with a guide member  311 ,  321  generally extending along the travel direction B. The guide members  311 ,  321  each configured to include a bent portion  3111 ,  3211  extending at a sharp angle, such as about 30-45°, relative to the travel direction B, and a straight portion  3112 ,  3212  connected to and merged with the bent portion  3111 ,  3211  and extending along the travel direction B. The respective straight portions  3112 ,  3212  may be connected to the corresponding bent portions  3111 ,  3211  with a sharp or rounded inner corner. Since the safety shutters  31 ,  32  are kept in generally parallel at all times by the locking bar  40 , the two guide members  311 ,  321  are similarly spaced apart in parallel by a fixed distance D at all times. Further, the safety shutters  31 ,  32  each includes a upper surface  312 ,  322  proximate to the top face panel  11  and a lower surface  313 ,  323  opposite to the upper surface  312 ,  322  and preferably facing away from and generally parallel to the top face panel  11 . Preferably, the safety shutters  31 ,  32  are tapered into a wedge-like form, so that the upper surface  312 ,  322  are each in the form of a slant surface inclined downwardly towards the lower surface  313 ,  323 . 
     The locking bar  40 , preferably made of dielectric material, is mounted in the housing  10  and extends along a direction traversing, preferably substantially perpendicular to, the travel direction B, as indicated by the arrow C. The locking bar  40  is held by the housing  10 , preferably confined in a compartment defined by the housing  10 , in a manner sildably movable in the traverse direction C but unmovable in the travel direction B. The locking bar  40  is provided with a first engagement portion  41  and a second engagement portion  42  separate from each other by the same distance D, so as to slidably engage the guide members  311 ,  321 . According to the embodiment disclosed herein, both of the guide members  311 ,  321  are configured in the form of a guide groove  311 ,  321  formed on the lower surfaces  313 ,  323  for receiving the engagement portions  41 ,  42  configured in the form of tabs  41 ,  42  extending upwardly from the locking bar  40 . Preferably, the guide grooves  311 ,  321  are each defined by two ribs extending on the lower surface  313 ,  323  in the travel direction B. The tabs  41 ,  42  each includes a side face  411 ,  421  inclined at the same angle as that of the bent portion  3111 ,  3211  relative to the travel direction B and adapted to abut against the bent portion  3111 ,  3211  when the safety shutters  31 ,  32  rest at their advancing position. By virtue of this abutment relationship, if the safety shutters  31 ,  32  move towards the locking bar  40  along the travel direction B, the inclined side faces  411 ,  421  would simultaneously receive an equal component force in the traverse direction C and, as a result, the locking bar  40  would be driven to move along the traverse direction C. More preferably, the locking bar  40  is further formed with a protrusion  43  between the tabs  41  and  42 . The protrusion  43  includes two end faces  431 ,  432  facing towards and adapted to slidably abut against side walls  315 ,  325  of the safety shutters  31 ,  32  perpendicular to the upper surfaces  312 ,  322  and the lower surfaces  313 ,  323 . 
     In some embodiments, the tabs  41 ,  42  are each configured in the form of a parallelogramoid body having four side faces as shown in  FIG. 4C , where the inclined side face  411 ,  421  and the opposite side face  413 ,  423  parallel thereto are arranged to incline relative to the travel direction B and abut against the bent portion  3111 ,  3211  when the safety shutters  31 ,  32  are at their advancing position. The side faces  412 ,  422  and the opposite faces  414 ,  424  are arranged to be generally parallel to the travel direction B and abut the respective straight portions  3112 ,  3212  during the period that the safety shutters  31 ,  32  are moving along the travel direction B. 
     The operation of the power connector  1  disclosed herein will now be described with reference to  FIGS. 5A-5D . When a two- or three-pin electric plug is being inserted into the power connector  1 , the pressing force of the live and neutral male contacts applied onto the upper slant surfaces  312 ,  322  along the insertion direction A will generate a component force in the travel direction B to urge the safety shutters  31 ,  32  away from the walls  341 ,  351 , against the biasing force applied by the biasing members  33 . Since the component forces applied onto the respective upper slant surfaces  312 ,  322  are approximately equal, the respective inclined side faces  411 ,  421  of the tabs  41 ,  42  are pushed evenly as a result of their abutment on the bent portions  3111 ,  3211 , thereby driving the locking bar  40  to move in the traverse direction C as the safety shutters  31 ,  32  move rearwards along the travel direction B. The protrusion  43  assists and stabilizes the whole sliding process by slidably abutting its end faces  431 ,  432  on the side walls  315 ,  325  of the safety shutters  31 ,  32 . As the safety shutters  31 ,  32  are moved to a retracted position shown in  FIGS. 5B  and SD, the power receptacles  111 ,  112  are fully opened and the tabs  41 ,  42  are brought in engagement with the straight portions  3112 ,  3212 . When the male contacts are removed from the power connector  1 , the safety shutters  31 ,  32  move back to the advancing position shown in  FIGS. 5A and 5C  to close the power receptacles  111 ,  112 , and the locking bar  40  returns as well. 
     According to the embodiment disclosed herein, the engagement between the tabs  41 ,  42  and the bent portion  3111 ,  3211  ensures that the respective tabs  41 ,  42  will get stuck in the bent portions  3111 ,  3211  if being driven alone. Therefore, if a user attempts to insert an object either into the neutral receptacle  111  alone, or into the live receptacle  112  alone, the safety shutters  31 ,  32  will remain staying at the advancing position. In either case, the safety shutters  31 ,  32  is jammed at the advancing position due to the engagement between the bent portions  3111 ,  3211  and the tabs  41 ,  42 . For example, in the case where the safety shutter  32  is pushed alone towards the locking bar  40 , the tab  42  receives a component force in the traverse direction C. The locking bar  40 , however, will be impeded from moving in the traverse direction C due to the abutment of the tab  41  against the inclined face of the bent portion  3111 , since the safety shutter  31 , without receiving any force in the travel direction B, is held at the advancing position. Thus, the safety shutters  31 ,  32  are only allowed to travel dependently of each other in the travel direction, and an unwanted or improper insertion of a single male contact of the plug into the power receptacles is prevented accordingly. 
     In the preferred embodiments, the upper slant surfaces  312 ,  322  are configured to incline at an angle of about 30 degree relative to the travel direction B, as shown in  FIG. 6 . 
     In some preferred embodiments, the power connector  1  disclosed herein further comprises a common grounding frame  50 . Desirably, the common grounding frame  50  is secured within the middle chamber of the interior cavity  13 . The common grounding frame  50  is preferably a single-piece element made of material with high electrical conductivity, preferably made of one or more conductive metals or metal alloys, such as brass or phosphor copper. The common grounding frame  50  can be fabricated by any process known in the art, such as metal stamping and punch pressing. As shown in  FIGS. 1 and 7A, 7B , the common grounding frame  50  includes one or more access portions  51  facing towards the top face panel  11  and a common grounding base  52  remote from the top face panel  11 , preferably facing towards the bottom face panel  12 . The access portions  51  each includes a resilient member for receiving and holding the grounding contact of a plug, which is preferably configured in the form of a resilient metal clip having a gripping part conforming in shape to the plug contact. The access portions  51  are registered with the grounding receptacles  113 - 116  formed on the top face panel  11 , so that they are adapted for receiving the grounding contact of the electric plug through the grounding receptacles  113 - 116  along the insertion direction A, thereby establishing electrical connection between the common grounding frame  50  and the electric plug. Among them, a Schuko access portion  511  is adapted to take the male grounding contact of a US, Danish or Israeli plug. The term “Schuko” as used herein refers to a system of AC power plugs and sockets that is defined as CEE 7/3 for the sockets and CEE 7/4 for the plugs by the European Commission for Conformity Testing of Electrical Equipment (CEE). According to the Standards, a Schuko plug features two round pins of 4.8 mm diameter (19 mm long, centers 19 mm apart) for the live and neutral contacts, plus two flat contact areas on the top and bottom side of the plug for protective earth. The gripping part  512  of the Schuko access portion  511  has two free ends extending upwardly and outwardly beyond the top face panel  11  through the Schuko grounding receptacle  113 , so as to constitute a flat Schuko contact  513 . The Schuko contact  513  is configured in the form of two metal plates lying on shoulder portions  117  surrounding the Schuko grounding receptacle  113  and adapted for engagement with the grounding contact of a CEE 7/4 Schuko plug. The shoulder portions  117  may be cut away a depth for anchorage of the Schuko contact  513 . More preferably, the Schuko contact  513  is built in a manner slightly protruding beyond the top face panel  11 , such as 1-10 mm higher than the surface of the top face panel  11 , so as to ensure good ground contact with the plug. 
     The Schuko access portion  511  is formed with a curved portion  5121  in the middle of the gripping part  512 , thereby gaining sufficient resilience to accept both of the 4.8 mm US ground pin and the 6.0 mm Denmark ground pin and then restore back to its original location and shape required by the Schuko grounding. 
     In a more preferred embodiment, the safety shutters  31 ,  32  are so arranged that they are driven to move towards the Schuko contact  513  in response to the insertion of an electric plug. It was unexpectedly found by the inventors that such arrangement facilitates the attachment of the flat ground contact of a Schuko CEE 7/4 plug onto the Schuko contact  513  by urging the safety shutters  31 ,  32  to push the plug towards the Schuko contact  513 . As a result, the shaking problem is reduced to the minimum, and the potential gap between the plug and the power connector is almost non-existent. 
     The common grounding frame  50  can be configured to include any combination of access portions  51  to receive plugs of desired specifications. In an alternative embodiment where the power connector  1  is not intended to receive a Schuko plug, the common grounding frame  50  is free of any Schuko contact for engagement with the grounding contact of the Schuko plug. In this case, the common grounding frame  50  does not have a constituting element extending outwardly beyond the top face panel  11 , as shown in  FIG. 7C . Two power connectors  1 , in which the common grounding frame is not provided with a Schuko contact, are shown in  FIGS. 7D and 7E . 
     The input portions  212 ,  222  and the common grounding base  52  are coupled to a variety of conductive couplers for electrical connection to an external power source, and the power connector disclosed herein can serve as a common architecture applicable to various forms of adapters and socket-outlets accordingly. 
     In one embodiment, the power connector disclosed herein is fabricated as a universal socket  1 ′ shown in  FIGS. 9A and 9B , and the conductive couplers thereof are each configured in the form of a wire holder  60 . The wire holder  60  is preferably a hollow metal tube formed at its open end with a blind wire bore  61  for receiving an electrical wire and further formed with a radially extending threaded hole  62  for receipt of a tightening screw  63  to hold down the electrical wire inserted into the wire bore  61 . It is well-known by those skilled in the art that there are many other types of wire holders that can be used herein, such as a wire clamp adapted to hold an electrical wire. 
     In another embodiment, the power connector disclosed herein is fabricated as a universal power strip shown in  FIG. 9 , in which a number of the universal sockets  1 ′ shown in  FIG. 8A  are held by a common dielectric chassis  70  and electrically connected in series to a power cord. 
     In an alternative embodiment, the power connector disclosed herein is fabricated as a universal adapter  1 ″ which comprises a plug part adapted for plugging into a domestic mains socket, in addition to the top face panel  11  at an opposite side adapted for receiving any of a variety of electric plugs. As shown in  FIG. 10A , the universal adapter  1 ″ comprises a number of conductive couplers configured in the form of plug contacts  81 ,  82  conforming to the domestic standards. According to the embodiment disclosed herein, the ground pin  81  is coupled to the common grounding base  52  by a rivet  83  integrally formed on the ground contact  81  as shown in  FIG. 10B , whereas the live and neutral pins  82  are similarly fastened to the input portions  212 ,  222  with a rivet  84  as shown in  FIG. 10C . 
     In yet an alternative embodiment, the power connector disclosed herein is fabricated as an all-in-one adapter kit, which comprises a universal socket  1 ′″ shown in  FIG. 11A  and a set of replaceable plug boards  90  adapted for detachable engagement with and electrical connection to the universal socket  1 ′″. The kit allows the user to interchange a plug board  90  exemplified in  FIG. 11B  with another plug part provided with a different type of plug pins. It is within the teachings of the present disclosure that the universal socket  1 ′″ may be combined with the replaceable plug boards  90  in any suitable manner to establish the intended electrical connection, such as snap-fit attachment, sliding engagement, and any other suitable releasable connection. In a more preferred embodiment, the universal socket  1 ′″ includes three conductive couplers. Two of them are arranged in direct wiring connection to the input portions  212 ,  222 , respectively, and extend outwardly beyond the bottom face panel  12  to constitute power terminals  16 . Desirably, the power terminals  16  are each configured as a vertical blade having an end bent into a horizontal plate  161  parallel to the bottom face panel  12 . The remaining one is in direct wiring connection to the common grounding base  52  and extends outwardly beyond the bottom face panel  12  to constitute a ground terminal  17 , preferably configured in the form of a metal stud. As exemplified in  FIG. 11B , the replaceable plug boards  90  are each formed with two power slots  91  for receiving the power terminals  16  and a ground slot  92  for receiving the ground terminal  17 . The power slots  91  are each provided at an end with an expanded opening  911  allowing entry of the horizontal plate  161 , and a narrow opening  912  at the opposite end merged with the expanded opening  911 , from which the horizontal plate  161  once inserted cannot be pulled out. The power slots  91  and the ground slot  92  are arranged in generally parallel relation to one another, so that the ground terminal  17  gets into the ground slot  92  with the entering of the power terminals  16  into the power slots  91  through the expanded opening  911 . Then, the power terminals  16  can be moved to slide along the power slots  91  from the ends  911  to the opposite ends  912  where they engage resilient power contacts  913  connected to the power blades  95  of the plug board  90 . As the power terminals  16  are brought in engagement with the resilient power contacts  913 , the ground terminal  17  is also brought to abut against a resilient ground contact  923  embedded in the ground slot  92  and connected to the ground pin  96  of the plug board  90 . 
     The engagement mechanism above may also be applied to the universal power strip shown in  FIG. 9 , as a means to couple the dielectric chassis  70  to the power cord  71  and establish electrical connection between the universal sockets  1 ′ and the power cord  71 . According to this embodiment, the input portions  212 ,  222  of the universal sockets  1 ′ are electrically connected in series to the power terminals, respectively, while the respective common grounding bases  52  are connected in series to the ground terminal. 
     In a preferable embodiment, the universal socket  1 ′″ is further provided with an error-proof mechanism for ensuring that the replaceable plug board  90  be engaged with the universal socket  1 ′″ only in a correct orientation. The error-proof mechanism may involve any male-female coupling mechanism known in the art, such as the engageable relationship between the flange  19  and the groove  99  shown in  FIGS. 11A-11B . 
     The all-in-one adapter kit may further comprise a polyhedron-shaped snap-in holder  110 , to which the universal socket  1 ′″ and the replaceable plug boards  90  are releasably attached to constitute a unitary assembly. In a preferred embodiment, the snap-in holder  111  is cuboid-shaped with five of its facets being configured to be complementary in shape to the universal socket  1 ′″ and the replaceable plug boards  90 , respectively, so that the all-in-one adapter kit, after assembled, becomes a pyramid-like packaging with high portability and compactness as shown in  FIG. 12 . 
     While the invention has been described with reference to the preferred embodiments above, it should be recognized that the preferred embodiments are given for the purpose of illustration only and are not intended to limit the scope of the present invention and that various modifications and changes, which will be apparent to those skilled in the relevant art, may be made without departing from the spirit and scope of the invention.