Abstract:
To prevent electrocution from improper connections through electrical outlets including Arc Fault Circuit Interrupters (commonly known as AFCI&#39;s), Ground Fault Circuit Interrupters (commonly known as GFCI&#39;s) and power strips, plugs of matching configuration should be used. For purposes of this application, “electrical outlet” or “receptacle outlet” have the same meaning as an “outlet”. When unattended, some children could be electrocuted by inserting metallic objects into electrical outlets. To control these incidents, it becomes necessary to provide outlets with a shutter device incorporated into the housing cover so that only plugs of matching configuration can be used. For purposes of this application, “childproof”, “tamper-proof” or “tamper-resistant” outlets are the same and refer to an outlet provided with a shutter device as the present invention. These shutter devices are typically incorporated into the outlet housing cover to resist tampering or entry of any object other than a plug of matching configuration.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     None. 
     FIELD OF THE INVENTION 
     The present invention relates to a tamper-resistant shutter device incorporated into an outlet housing cover to prevent insertion of any object into an electrical outlet except a plug of matching configuration. 
     BACKGROUND OF THE INVENTION 
     Electrical outlets including AFCI, GFCI, power strips, and extension cords are used to connect portable appliances and other electrical equipment. Most of the commonly available outlets are not protected from improper connections and entry of foreign metallic objects causing a major concern for the safety of users especially children or inexperienced individuals. To control said improper connections, a mechanism, device or assembly so configured to resist the entry of any object other than a plug that matches the configuration and geometry of the outlet could be incorporated into the outlet housing cover. In North America, outlets are configured according to their voltage and current ratings and referred to as the National Electrical Manufacturers Association configurations or commonly known as NEMA configurations. The most common household electrical outlet configurations are the NEMA 1-15R, 2-15R, 2-20R, 5-15R  50 , 5-20R  51 , 6-15R  52  and 6-20R  53 , respectively for 125V/15A ungrounded, 250V/15A ungrounded, 250V/20A ungrounded, 125V/15A with ground, 125V/20A with ground, 250V/15A with ground and 250V/20A with ground. Electrical plugs NEMA 1-15P  43 , 2-15P  44 , 2-20P  45  may be used with outlets of the same configuration with or without ground. For purposes of this patent application, the term “ungrounded” refers to a plug or a receptacle outlet without ground connection, whereas the term “grounded” refers to a plug or receptacle outlet with ground connection. 
     There are electrical outlets provided with tamper-resistant shutters commercially available, however, most of them are limited to two configurations including the most common NEMA 1-15R and 5-15R  50 . Most prior art designs do not provide total tampering protection for outlets with ground. The NEMA 1-15R is similar to the NEMA 5-15R  50  except that it has no ground connection. 
     With the limited protection and features offered by prior art designs, there is always a possibility to develop a better and more effective tamper-resistant shutter device for electrical outlets as with the present invention. 
     The present invention would apply to at least 7 different electrical outlet configurations including NEMA 1-15R, 2-15R, 2-20R, 5-15R  50 , 5-20R  51 , 6-15R  52  and 6-20R  53 . For purposes of this patent application, specific NEMA outlet configurations are used, however, the same principles, methods and techniques may be used for other configurations including those used in other countries and standards. 
     The present invention affords protection for multiple outlet configurations and saves production costs and tooling. The present invention ensures an effective tamper-resistant protection by allowing only plugs of matching configuration to be used with the outlet, avoiding electrocution or other harmful incidents. For someone to use anything but the proper plug, it would require knowledge of the operating mechanisms of the present invention to articulate the geometry of a matching plug. The present invention employs multiple levels of protection through interlocked mechanisms so the device would only operate when both plug blades are inserted simultaneously. In case of a grounded plug, the present invention includes a ground pin lockout release mechanism  34  so the shutters to the electrical outlet only open when a matching plug configuration is used. 
     U.S. Pat. No. 7,452,221B1 (November/2008 Oddsen et al) disclosed a shutter device for a NEMA 5-15R electrical outlet different from the present invention which is designed to accommodate multiple configurations with and without ground. The Oddsen et al patent also refers to a shutter device relying on a sliding and pivotal movement of shutter members through a side frame to position the openings in the shutter plate with the outlet contacts. This is different from the present invention which uses wedge-driven positioning members to release locking mechanisms. 
     U.S. Pat. No. 7,312,394B1 (December/2007 Weeks et al) disclosed a shutter device for a limited configuration different from the present invention which accommodates multiple configurations, with and without ground. The Weeks et al patent also refers to a shutter device with a stationary positioning member and the other moving in the same plane but in opposite direction. This is different from the present invention which uses wedge-driven positioning members to release locking mechanisms for the plug to be used with the outlet. The ground pin release mechanism disclosed in the Weeks et al patent is offset from the center of the assembly due to space limitations, whereas the present invention employs a ground-pin lockout release mechanism directly at the centerline of the shutter frame. This is made possible by the space-saving configuration disclosed in the present invention. 
     U.S. Pat. No. 7,868,719B2 (January/2011 Bazayev et al) disclosed a shutter device for a limited outlet configuration different from the present invention which is designed to accommodate multiple configurations, with and without ground. The Bazayev et al patent also refers to a shutter device with two similar sliding plates moving in unison to align the plug blades with the receptacle outlet contact points which is different from the present invention which uses wedge-driven positioning members to release locking mechanisms to open access holes for the plug to be used with the outlet. The Bazayev et al patent also did not disclose any provision for ground-pin lockout release mechanism, which is provided with the present invention. 
     US2010/0041259 A1 (February/2010 Ni) disclosed a shutter device for NEMA 5-15R and 5-20R electrical outlets different from the present invention which is designed to accommodate multiple configurations, with and without ground. The Ni patent refers to a shutter device with independently movable spring-activated elements which differ from the present invention using wedge-driven positioning members to release locking mechanisms for the plug to be used with the outlet. The Ni patent did not disclose any provision for ground-pin lockout release mechanism, which is provided with the present invention. 
     US2009/0236115 A1 (September/2009 Li) disclosed a shutter device for a NEMA 5-15R electrical outlet different from the present invention which is designed to accommodate multiple configurations, with and without ground. The Li patent refers to a shutter device with two opposing spring-activated members overlaid against each other through their side openings to resist tampering. The present invention is framed and wedge-driven positioning members are used to release locking mechanisms to access the outlet. The Li patent did not disclose any provision for ground-pin lockout release mechanism which is provided with the present invention. 
     SUMMARY OF THE INVENTION 
     The present invention is focused on providing a safe, reliable and cost-effective means to avoid dangerous access to electrical outlets by children or inexperienced individuals. This is possible through the use of a tamper-resistant shutter device incorporated into an outlet housing cover. The mechanism may be used as accessory for outlet housing covers for AFCI, GFCI, power strips, extension cords and portable outlets. The present invention ensures that outlet contacts remain covered and only become accessible when a plug that matches the outlet configuration is used. To withstand reasonable usage and allow independent assembly, the shutter device is framed. 
     The present invention employs multiple interlocked wedge-driven positioning members to ensure a total tamper-resistant protection by allowing only plugs of matching configuration to be used with the electrical outlet. This poses a challenge for a child or any user to tamper with the device, avoiding electrocution or other harmful incidents. For someone to use anything but the proper plug, it would require knowledge of the operating mechanism of the present invention to articulate the geometry of the plug blades and ground pin. The wedge-driven positioning members ensure the shutters would only open when both blades of the plug are inserted simultaneously. The cover to the access holes on the frame only opens when the shutters are displaced a calculated distance to align with the outlet contact points. These wedge-driven positioning members are maintained in a default “closed position” by springs and stoppers when no plug is used with the outlet. 
     Certain standard NEMA outlet configurations are cited for reference in the present invention, however, adopting the same principles, methods or techniques for other configurations or styles used in other countries and standards will attain the same objective. 
     Not limiting the scope of the present invention, one skilled in the art may recognize the methods disclosed could apply to any other applications not mentioned herein with similar objectives. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows some of the most common NEMA outlets with matching plug configurations, with and without ground, which the present invention could be used on. 
         FIG. 2  shows the present invention using frame  1 A for NEMA 1-15R and 5-15R  50  outlet configurations with the ground pin lockout release mechanism  34  enabled. In the figure, the outlet  51  is a combination NEMA 5-15R and 5-20R and could be used with either plug configuration NEMA 5-15P or 5-20P. A NEMA 1-15P plug may be used on either outlet  50  or  51 . 
         FIG. 3  shows the present invention using frame  1 A for NEMA 1-15R and 5-15R  50  outlet configurations with the ground pin lockout release mechanism  34  disabled. In this mode, the lockout insert  35  is applied to restrict movement of the ground pin lockout release mechanism  34 . 
         FIG. 4  shows the layout of the main shutter sub-assembly  100  of the present invention using frame  1 A. 
         FIG. 5  shows the frame ( 1 A) of the present invention for NEMA 1-15R and 5-15R  50  outlet configurations. 
         FIG. 6  shows an open view of the present invention using frame  1 A incorporated into a receptacle outlet housing cover for NEMA 1-15R and 5-15R  50  configurations. 
         FIG. 7  shows multiple views of the present invention using frame  1 A incorporated into a receptacle outlet housing cover used with a NEMA 1-15P  43  plug. 
         FIG. 8  shows the present invention using frame  1  for electrical outlet configurations NEMA 1-15R, 2-15R, 2-20R, 5-15R  50 , 5-20R  51 , 6-15R  52  and 6-20R  53  with the ground pin lockout release mechanism  34  enabled. 
         FIG. 9  shows the present invention using frame  1  for electrical outlet configurations NEMA 1-15R, 2-15R, 2-20R, 5-15R  50 , 5-20R  51 , 6-15R  52  and 6-20R  53  with the ground pin lockout release mechanism  34  disabled. 
         FIG. 10  shows a layout of the main shutter sub-assembly  100 , the secondary shutter sub-assembly  200 , and the ground pin lockout release mechanism  34  of the present invention using frame  1 . 
         FIG. 11  shows the frame  1  of the present invention for electrical outlet configurations NEMA 1-15R, 2-15R, 2-20R, 5-15R  50 , 5-20R  51 , 6-15R  52  and 6-20R  53 . 
         FIG. 12  shows multiple views of the main shutter sub-assembly  100  of the present invention. 
         FIG. 13  shows the isometric view of the main shutter sub-assembly  100  of the present invention. 
         FIG. 14  shows multiple views of the secondary shutter sub-assembly  200  of the present invention. 
         FIG. 15  shows the isometric view of the secondary shutter sub-assembly  200  of the present invention. 
         FIG. 16  shows the wedge-driven positioning members  7 A and  7 B of the main shutter sub-assembly  100  used in the present invention. 
         FIG. 17  shows the locking mechanism  16  of the main shutter sub-assembly  100  used in the present invention. 
         FIG. 18  shows the secondary shutter sub-assembly  200  wedge-driven positioning members  26 A and  26 B used in the present invention. 
         FIG. 19  shows multiple views of the ground pin lockout release mechanism  34  used in the present invention. 
         FIG. 20  shows an open view of the present invention with frame  1  incorporated into a receptacle outlet housing cover for NEMA configurations 1-15R  51 , 2-15R  52 , 2-20R  53 , 5-15R  50 , 5-20R  51 , 6-15R  52  and 6-20R  53  plugs. 
         FIG. 21  shows multiple views of the present invention with frame  1  incorporated into a receptacle outlet cover and used with a NEMA 5-15P  46  plug. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     References will now be made in detail to describe the exemplary embodiments of the present invention, which are illustrated in the accompanying drawings. Details disclosed herein are not to be interpreted as limiting, but rather as basis for the claims and teaching one skilled in the art how the present invention could be employed in any appropriately detailed system, structure or manner. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like components, or functions. 
       FIG. 1  shows some of the most common NEMA outlets with matching plug configurations, with and without ground, which the present invention could be used with. The typical NEMA 1-15P  43  plug configuration employs two blades with the same geometry, or two blades of different width to distinguish line and neutral connections, in similar orientation with the body of the plug. The other configurations are for circuits with ground connections, also referred to as “grounded circuits”, or “grounded plugs”, or “grounded receptacles”. This includes NEMA 5-15P  46 , 5-20P  47 , 6-15P  48  and 6-20P  49 , all of which are with a ground pin and uses blades of the same geometry but in different orientation to the body of the plug. The NEMA 1-15P  43 , 2-15P  44  and 2-20P  45  plugs could only be used with grounded outlet configurations when the ground pin lockout release mechanism  34  of the present invention is disabled. 
       FIG. 2  shows the present invention as designed for outlets of similar configuration as the NEMA 1-15R and NEMA 5-15R  50  with the ground pin lockout release mechanism  34  enabled. When used for these outlet configurations only, a version of the tamper-resistant shutter device could use a short frame  1 A with the main shutter sub-assembly  100  and the ground pin lockout release mechanism  34 . 
     While the device is in a “shutter close”, or “default” position, or when no plug is inserted, the main shutter sub-assembly  100  and the ground pin lockout release mechanism  34  are in the following state:
         1. Main shutter sub-assembly  100 :
           a) The wedge-driven positioning members  7 A and  7 B are biased by springs  14 A and  14 B away from each other where the holes  2 C and  2 D on frame  1 A are covered,   b) The stopper plates  22 A and  22 B are locked with each other,   c) The wedge-shaped pins  12 A and  12 B are out of the slider openings  19  and  20 ,   d) The bottom portion of  7 A and  7 B are covering slots  2 C and  2 D of frame  1 A.   
           2. Ground pin lockout release mechanism  34 :
           a) The wedge-driven positioning member  34  is biased outside frame  1 A by spring  25  secured between the holder  42  and the stopper plate  22 A through the retaining pin  23 ,   b) The sloped surface  39  of the wedge-driven positioning member  34  is positioned within the ground pin inlet opening on the outlet cover,   c) The stoppers  41 A and  41 B are lined up with the stoppers  13 A and  13 B on the wedge-driven positioning members  7 A and  7 B.   
               

       FIG. 3  shows the present invention used with outlet configurations NEMA 1-15R and NEMA 5-15R  50  with the ground pin lockout release mechanism  34  disabled. For these outlet configurations, a variation of the tamper-resistant shutter device uses frame  1 A with the main shutter sub-assembly  100  and the ground pin lockout release mechanism  34 . 
       FIG. 4  shows the main shutter sub-assembly  100  layout using frame  1 A. Some parts of the main shutter sub-assembly  100  may be made integral to the frame  1 A. 
       FIG. 5  shows the frame  1 A of the present invention used with outlet configurations NEMA 1-15P  51  and 5-15R  50  plugs. Since these plug configurations have their blades in the same orientation, it is not necessary to have the secondary shutter sub-assembly  200  and therefore possible to use a shorter frame  1 A. 
       FIG. 6  shows an open view of the present invention with frame  1 A incorporated into a receptacle outlet housing cover for use with NEMA 1-15P  43  and 5-15P  46  plugs. 
       FIG. 7  shows multiple views of the present invention with frame  1 A incorporated into a receptacle outlet cover and used with a NEMA 1-15P  43  plug. 
     When a plug such as NEMA 1-15P is used with the outlet with the ground pin lockout release mechanism  34  disabled, the following movements occur subsequently on the main shutter sub-assembly  100 :
         a) The plug blades initially make contact with the wedge-driven positioning members  7 A and  7 B,   b) The blades are pushed in through the slopes  9 A and  9 B, gradually causing  7 A and  7 B to move inward and towards each other,   c) The wedge-shaped pins  12 A and  12 B move inward and push the stopper plates  22 A and  22 B sideward and away from each other, fully opening the hole  21 ,   d) The pin  11 A and its mating part  11 B engage with each other through the hole  21 ,   e) The wedge-driven positioning members  7 A and  7 B reach their maximum displacement defined by half the distance between the plug blades,   f) The hole sections  2 A and  2 B on the shutter frame  1  open to allow the plug blades to be used with the electrical outlet,   g) The ground pin lockout release mechanism  34  remains in its default “shutter close” position.       

     Pulling out a plug such as a NEMA 1-15P from the outlet with the ground pin lockout release mechanism  34  disabled, causes the main shutter sub-assembly  100  to return to its “default” or “shutter close” position by reversing the sequence outlined above. 
       FIG. 8  shows the present invention with frame  1  used with electrical outlet configurations NEMA 1-15R, 2-15R, 2-20R, 5-15R  50 , 5-20R  51 , 6-15R  52  and 6-20R  53  with the ground pin lockout release mechanism  34  enabled. To accommodate all these plug configurations, frame  1  is used with the present invention. 
     While the tamper-resistant shutter device is in a “shutter close”, or “default” position, or when no plug is inserted, the main shutter sub-assembly  100 , secondary shutter sub-assembly  200 , and the ground pin lockout release mechanism  34  are in the following state:
         1. Main shutter sub-assembly  100 :
           a) The wedge-driven positioning members  7 A and  7 B are biased by spring  14  away from each other where the holes  2 A,  2 B,  3 A and  3 B on the frame  1  are covered,   b) The stopper plates  22 A and  22 B are locked with each other,   c) The tips of the wedge-shaped pins  12 A and  12 B are out of the slider openings  19  and  20 ,   d) The slots  10 A and  10 B of the main wedge-driven positioning members  7 A and  7 B are locked with the stoppers  30 C and  30 D of the secondary shutter sub-assembly  200 ,   e) The bottom portions of  7 A and  7 B are covering slots  2 A and  2 B of frame  1 .   
           2. Secondary shutter sub-assembly  200 :
           a) The wedge-driven positioning members  26 A and  26 B are biased towards one end of the frame by the springs  33 A and  33 B,   b) The openings  27 A and  27 B are directly above a closed section of frame  1 ,   c) The openings  3 A and  3 B are covered by the lower portion of the sloped surfaces  28 A and  28 B of the wedge-driven positioning members  26 A and  26 B,   d) The stoppers  30 C and  30 D are locked by the slots  10 A and  10 B of the wedge-driven positioning members  7 A and  7 B of the main shutter sub-assembly  100 ,   e) The lower portion of the sloped surface of the wedge-driven positioning members  7 A and  7 B of the main shutter sub-assembly  100  are tucked under sections  30 A,  30 B,  31 A and  31 B.   
           3. Ground pin lockout release mechanism  34 :
           a) The wedge-driven positioning member  34  is biased outside the frame by spring  25  secured between the holder  42  and the stopper plate  22 A through the retaining pin  23 ,   b) The sloped surface  39  of the wedge-driven positioning member  34  is positioned within the ground pin inlet opening,   c) The stoppers  41 A and  41 B are lined up with the stoppers  13 A and  13 B on the wedge-driven positioning members  7 A and  7 B,   
               

       FIG. 9  shows the present invention with frame  1  used with electrical outlet configurations NEMA 1-15R, 2-15R, 2-20R, 5-15R  50 , 5-20R  51 , 6-15R  52  and 6-20R  53  with the ground pin lockout release mechanism  34  disabled. The lockout insert  35  is in place, restricting any movement of the ground pin lockout release mechanism  34 . 
       FIG. 10  shows the main shutter sub-assembly  100 , the secondary shutter sub-assembly  200 , and the ground pin lockout release mechanism  34  layout in the present invention using frame  1 . 
       FIG. 11  shows the frame  1  of the present invention used with electrical outlet configurations NEMA 1-15R, 2-15R, 2-20R, 5-15R  50 , 5-20R  51 , 6-15R  52  and 6-20R  53 . 
       FIGS. 12 to 15  shows different views of the main shutter sub-assembly  100  and the secondary shutter sub-assembly  200  as used in the present invention. 
       FIGS. 16 and 17  shows the main and secondary wedge-driven positioning members  7 A,  7 B,  26 A and  26 B used in the present invention. 
       FIGS. 18 and 19  shows details of the secondary wedge-driven positioning members  26 A and  26 B and the ground pin lockout release mechanism  34  used in the present invention. 
       FIG. 20  shows an open view of the present invention with frame  1  incorporated into a receptacle outlet housing cover for NEMA 1-15R, 2-15R, 2-20R, 5-15R  50 , 5-20R  51 , 6-15R  52  and 6-20R  53 . 
       FIG. 21  shows multiple views of the present invention with frame  1  incorporated into a receptacle outlet cover with a NEMA 5-15P  46  plug. 
     When a plug is used on outlet configuration NEMA 2-15R, 2-20R, 5-15R  50 , 5-20R  51 , 6-15R  52 , or 6-20R  53  with the ground pin lockout release mechanism  34  disabled, the following movements occur subsequently on the main shutter sub-assembly  100  and the secondary shutter sub-assembly  200 :
         a) The plug blades initially make contact with the wedge-driven positioning members  7 A and  7 B,   b) The blades are pushed in through the slopes  9 A and  9 B, gradually causing  7 A and  7 B to move inward and towards each other,   c) The slots  10 A and  10 B of the wedge-driven positioning members  7 A and  7 B disengages with the stoppers  30 C and  30 D,   d) The plug blades are pushed in through the sloped surfaces  28 A and  28 B cause the sideward displacement of wedge-driven positioning members  26 A and  28 B,   e) The wedge-shaped pins  12 A and  12 B move inward pushing the stopper plates  22 A and  22 B sideward and away from each other, fully opening the hole  21 ,   f) The pin  11 A and its mating part  11 B engage with each other through the hole  21 ,   g) The wedge-driven positioning members  7 A and  7 B reach their maximum displacement defined by half the distance between the plug blades,   h) The slots  27 A and  27 B finally align with the openings  3 A and  3 B on frame  1 ,   i) The hole sections  2 A and  2 B on the shutter frame  1  are finally uncovered,   j) The plug blades get fully engaged with the electrical outlet.       

     Pulling out a plug such as NEMA 5-15P  46 , 5-20P  47 , 6-15R  48 , or 6-20R  49  from the outlet in which the ground pin lockout release mechanism  34  is disabled, causes the main shutter sub-assembly  100  and the secondary shutter sub-assembly  200  to return to their default or “shutter close” positions by reversing the sequence outlined above. 
     When a plug is used on outlet configurations NEMA 5-15R  50 , 5-20R  51 , 6-15R  52  and 6-20R  53  with the ground pin lockout release mechanism  34  enabled, the following movements occur subsequently on the main shutter sub-assembly  100 , secondary shutter sub-assembly  200 , and the ground pin lockout release mechanism  34 :
         a) The ground pin pushes the wedge-driven positioning member  34  to a defined position,   b) The stoppers  41 A and  41 B move in so that openings  40 A and  40 B line up with the stoppers  13 A and  13 B on the wedge-driven positioning members  7 A and  7 B, allowing them free movement,   c) The plug blades make contact with the wedge-driven positioning members  7 A and  7 B,   d) The blades are pushed in through the slopes  9 A and  9 B, gradually causing  7 A and  7 B to move inward and towards each other,   e) The slots  10 A and  10 B of the wedge-driven positioning members  7 A and  7 B disengage from the stoppers  30 C and  30 D,   f) The plug blades being pushed in through the sloped surfaces  28 A and  28 B cause the sideward displacement of wedge-driven positioning members  26 A and  26 B,   g) The wedge-shaped pins  12 A and  12 B move inward and push the stopper plates  22 A and  22 B sideward and away from each other, fully opening the hole  21 ,   h) The pin  11 A and its mating part  11 B engage through the hole  21 ,   i) The wedge-driven positioning members  7 A and  7 B reach their maximum displacement defined by half the distance between the plug blades,   j) The slots  27 A and  27 B finally align with the openings  3 A and  3 B on frame  1 ,   k) The hole sections  2 A and  2 B on the shutter frame  1  are finally uncovered,   l) The plug blades get fully engaged with the electrical outlet.       

     Pulling out a plug such as NEMA 5-15P  46 , 5-20P  47 , 6-15P  48 , or 6-20R  49  from the outlet with the ground pin lockout release mechanism  34  enabled causes the main shutter sub-assembly  100 , secondary shutter sub-assembly  200 , and the ground pin lockout release mechanism  34  to return to their default or “shutter close” positions by reversing the sequence outlined above.