Abstract:
The present invention is directed to an assembly that includes a shutter having an interface portion coupled to a railed guidance structure so that the shutter rides the railed guidance structure from a return position to an open position in response to being engaged by the plurality of plug blades; the interface portion and the railed guidance structure allowing the shutter to rotationally align with the ends of the plug blades in response to an asymmetry in respective lengths of the plug blades. The open position permits electrical engagement of the plurality of plug blades with the plurality of receptacle contacts. The shutter is also directed from the return position to a blocking position in response to being engaged by a foreign object via one of the plurality of receptacle openings to prevent the foreign object from engaging the set of receptacle contacts.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to electrical wiring devices, and particularly to tamper-resistant electrical wiring devices. 
         [0003]    2. Technical Background 
         [0004]    Electrical power is provided to users by way of electrical distribution systems that typically include electrical wiring from a utility power source to a breaker panel disposed in a house, building or some other facility. The breaker panel distributes AC power to one or more branch electric circuits installed in the structure. The electric circuits may typically include one or more electrical wiring devices that regulate, monitor or provide AC power to other devices. Each electrical wiring device is equipped with electrical terminals that provide a means for connecting the device to the source of AC power and a means for connecting the device to a load. Specifically, line terminals couple the device to the source of AC electrical power, whereas load terminals couple power to the load. Load terminals may also be referred to as “feed-through” or “downstream” terminals because the wires connected to these terminals may be coupled to a daisy-chained configuration of receptacles or switches. 
         [0005]    Thus, an electric circuit may include many different electrical wiring devices disposed at various locations throughout a structure. Outlet receptacles, switches and protective devices are examples or types of electrical wiring devices. Ground fault circuit interrupters (GFCIs), and are fault circuit interrupters (AFCIs) are examples of protective devices in electric circuits. Switches, protective devices and other types of electrical devices are often provided in combination with receptacles. For example, outlet receptacles are disposed in duplex receptacles, raceways, multiple outlet strips, power taps, extension cords, light fixtures, appliances, and the like. When the wiring terminations of these devices (i.e., wiring terminals, plugs, etc.) of these devices are connected to the electrical distribution system, the receptacle contacts may be energized. When the power cord of an electrical appliance is inserted into the receptacle outlet, the device is also energized. 
         [0006]    When a foreign object is inserted into a receptacle opening it may represent a safety hazard. Specifically, young children and toddlers are known to have a proclivity toward inserting objects such as paper clips or screwdriver blades into receptacle contact openings. (This should be a cause for alarm, especially in light of the fact that, e.g., GFCIs are configured to trip in response to a mere 6 mA current). Even a small current (in the mA range) passing through a human body to ground can result in an electric shock, burns, or electrocution (a fatal shock event). As a result, the use of shuttered openings in electrical receptacles has long been in use in an attempt to prevent the insertion of foreign objects into the receptacle contact openings. One drawback to this approach relates to the ineffectiveness of related art designs. In many conventional designs, when objects are placed into both openings, the shutter will typically operate, exposing the child to a shock hazard. What is needed is a shutter mechanism that only opens when an actual corded plug is inserted into the receptacle. 
         [0007]    Another drawback to this approach relates to the complexity of related art shutters. Many shutter designs comprise multiple parts and spring elements. For example, in one conventional approach that has been considered, the shutter must be intricately installed within a base platform (by hand) after positioning a delicate leaf spring element within the base. The cost and time of assembling the shutter mechanism, and the space taken up by their multiple parts, limit the usage of these designs. Moreover, automated environments often generate vibrations and mechanical forces that tend to introduce failure modes. Specifically, vibrations tend to cause the leaf spring to become dislodged or otherwise become separated from the platform. In addition, when objects are inserted into the receptacle opening, the shutter is forced to press against the leaf spring while moving upwardly and downwardly within the base platform. This type of movement increases the likelihood that the leaf spring will be dislodged. Once this happens, the receptacle device is either inoperable or unprotected. 
         [0008]    What is needed is a shutter assembly that is configured to operate smoothly (and robustly) even when foreign objects or uneven plug blades are forcefully inserted. What is also needed is relatively simple protective shutter assembly that is easy to install within an electrical wiring device. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention addresses the needs described above by providing a shutter assembly that is configured to operate smoothly (and robustly) even when foreign objects or uneven plug blades are forcefully inserted and robustly. The present invention also provides a relatively simple protective shutter assembly that is easy to install within an electrical wiring device. 
         [0010]    One aspect of the present invention is directed to an electrical device that includes a housing having a front cover coupled to at least one body member. The front cover includes a plurality of receptacle openings in a major front surface thereof. The plurality of receptacle openings is configured to receive a plurality of plug blades of a corded electrical plug. The at least one body member includes at least one set of receptacle contacts having a hot receptacle contact and a neutral receptacle contact configured to mate with the plurality of plug blades when the corded electrical plug is inserted into the plurality of receptacle openings. A set of electrical terminations is accessible via at least one aperture in the housing, the at least one set of receptacle contacts being configured to receive electrical power from the at least a portion of the set of electrical terminations. A guidance structure corresponding to the at least one set of receptacles is coupled to the front cover, the guidance structure including a first guidance portion and a second guidance portion. A shutter assembly includes a shutter element coupled to the first guidance portion in a return position when not engaged by an object and rotatable about the first guidance portion from the return position to a shutter blocking position in response to being engaged by an object via one of the plurality of receptacle openings. The object is prevented from obtaining access to the at least one set of receptacle contacts in the blocking position. The shutter element is translated from the return position on the first guidance portion to an open position on the second guidance portion in response to being engaged by the plurality of plug blades via the plurality of receptacle openings. The shutter is coupled to the guidance structure so that the shutter rotationally self-aligns to the plurality of plug blades when the shutter element is translated from the return position to the open position wherein the plurality of plug blades are allowed to mate with the hot receptacle contact and the neutral electrical contact, respectively. 
         [0011]    In one embodiment of the device, the shutter element is configured to rotationally self-align with end portions of the plurality of plug blades in response to an asymmetry in respective lengths of the plurality of plug blades. 
         [0012]    In one embodiment of the device, the guidance structure includes a first rail and a second rail configured to couple the shutter element therebetween, each of the first rail and the second rail includes a first rail portion extending from an interior major surface of the front cover in a substantially perpendicular direction to a pivot position to form the first guidance portion, each of the first rail and the second rail further includes a second rail portion extending from the pivot position at a predetermined angle relative the first rail portion to form the second guidance portion. 
         [0013]    In one version of the embodiment, the predetermined angle is greater than about thirty five degrees. 
         [0014]    In one embodiment of the device, the shutter element includes a first major surface disposed on one side thereof and configured to be engaged by the plurality of plug blades, the shutter element further includes a second major surface disposed on a second side thereof, the first major surface being substantially parallel to the second major surface. 
         [0015]    In one embodiment of the device, the shutter element includes a first major surface configured to be engaged by the plurality of plug blades, the shutter element further includes a first lateral rib portion disposed at a first edge of the first major surface and a second lateral rib portion disposed at a second edge of the first major surface parallel to the first edge, the first lateral rib portion and the second lateral rib portion being configured to prevent the first major surface from abutting an interior major surface of the front cover when the shutter assembly is disposed in the return position. 
         [0016]    In one version of the embodiment, the shutter element is configured to move from the return position to the translational portion via the pivot position when the shutter element is engaged by the plurality of plug blades. 
         [0017]    In one embodiment of the device, the guidance structure is configured as a yoke structure, the yoke structure includes a first railed bearing portion substantially disposed in parallel with a second railed bearing portion. 
         [0018]    In one version of the embodiment, the shutter element includes a first lateral opening and a second lateral opening configured to be coupled to the yoke structure, the first lateral opening includes a first substantially radial bearing interface and the second lateral opening includes a second substantially radial bearing interface configured to ride the first railed bearing portion and the second railed bearing portion, respectively, from substantially the return position to the open position in response to being engaged by the plurality of plug blades. 
         [0019]    In one embodiment of the device, the shutter element includes an aperture configured to allow one of the plurality of plug blades to pass through in the open position. 
         [0020]    In one embodiment of the device, the shutter element includes a seat portion configured to accommodate a spring, the spring being disposed between the seat portion and an anti-probing portion of the front cover. 
         [0021]    In one version of the embodiment, the spring is selected from a group of springs that include a torsion spring or a compression spring. 
         [0022]    In one embodiment of the device, the guidance structure is an integrally molded feature of an interior surface of the front cover. 
         [0023]    In one embodiment of the device, the housing includes a wiring device housing, a duplex receptacle housing, a decorator housing, an extension cord housing, a multiple outlet strip housing, a combination receptacle and switch housing. 
         [0024]    In one embodiment, the device further includes a protection circuit, a ground fault circuit interrupter, an arc fault circuit interrupter, or a surge protective device. 
         [0025]    In another aspect, the present invention is directed to an electrical device that includes a housing having a front cover coupled to at least one body member. The front cover includes a plurality of receptacle openings in a major front surface thereof, the plurality of receptacle openings being configured to receive a hot plug blade and a neutral plug blade of a corded electrical plug. The at least one body member includes at least one set of receptacle contacts having a hot receptacle contact and a neutral receptacle contact configured to mate with the hot plug blade and a neutral plug blade, respectively, when the corded electrical plug is inserted into the plurality of receptacle openings. A set of electrical terminations is accessible via at least one aperture in the housing, the at least one set of receptacle contacts being configured to receive electrical power from the at least a portion of the set of electrical terminations. A railed guidance structure corresponding to the at least one set of receptacle contacts is coupled to the front cover. A shutter assembly includes a shutter element having an interface portion coupled to the railed guidance structure so that the shutter element rides the railed guidance structure from a return position to an open position in response to being engaged by the plurality of plug blades. The interface portion and the railed guidance structure are configured to allow the shutter element to rotationally align with end portions of the plurality of plug blades in response to an asymmetry in respective lengths of the plurality of plug blades. The open position permits electrical engagement of the plurality of plug blades with the plurality of receptacle contacts. The shutter element is directed from the return position to a blocking position in response to being engaged by an object via at least one of the plurality of receptacle openings to prevent the object from obtaining access to the at least one set of receptacle contacts. 
         [0026]    In one embodiment of the device, the shutter element includes a first major surface disposed on one side thereof and configured to be engaged by the plurality of plug blades, the shutter element further includes a second major surface disposed on a second side thereof, the first major surface being substantially parallel to the second major surface. 
         [0027]    In one embodiment of the device, the shutter element includes a first major surface configured to be engaged by the plurality of plug blades, the shutter element further includes a first lateral rib portion disposed at a first edge of the first major surface and a second lateral rib portion disposed at a second edge of the first major surface parallel to the first edge, the first lateral rib portion and the second lateral rib portion being configured to prevent the first major surface from abutting an interior major surface of the front cover when the shutter assembly is disposed in the return position. 
         [0028]    In one embodiment of the device, the shutter element is configured to rotate about a first rail portion of the railed guidance structure when moving from the return position into the blocking position in response to being engaged by the object. 
         [0029]    In one version of the embodiment, the shutter element is configured to be translated from the first rail portion to a second rail portion of the railed guidance structure when moving from the return position to the open position when the shutter element is engaged by the plurality of plug blades. 
         [0030]    In one version of the embodiment, the railed guidance structure includes a yoke structure coupled to the front cover, the yoke structure including a first railed bearing portion substantially disposed in parallel with a second railed bearing portion. 
         [0031]    In one version of the embodiment, the shutter element includes a first indented opening and a second indented opening coupled to the yoke structure. The first indented opening includes a first substantially radial bearing interface and the second indented opening includes a second substantially radial bearing interface configured to ride the first railed bearing portion and the second railed bearing portion, respectively, from substantially the return position to the open position in response to being engaged by the plurality of plug blades, the shutter being coupled to the railed guidance structure so that the shutter rotationally self-aligns to the plurality of plug blades when the shutter element is translated from the return position to the open position wherein the plurality of plug blades are allowed to mate with the hot receptacle contact and the neutral electrical contact, respectively. 
         [0032]    In one version of the embodiment, each of the first railed bearing portion and the second railed bearing portion include a first portion extending from an interior major surface of the front cover in a substantially perpendicular direction to a pivot position. Each of the first railed bearing portion and the second railed bearing portion further extend from the pivot position at a predetermined angle relative the first railed bearing portion such that the shutter element translates from the return position to the open position in a direction parallel to the interior major surface of the front cover a distance substantially equal to a width of one of the plurality of receptacle openings. 
         [0033]    In one version of the embodiment, the predetermined angle is greater than about thirty five degrees. 
         [0034]    In one embodiment of the device, the shutter element includes an aperture configured to allow one of the plurality of plug blades to pass through in the open position. 
         [0035]    In one version of the embodiment, the shutter element includes a seat portion configured to accommodate a spring, the spring being disposed between the seat portion and an anti-probing portion of the front cover. 
         [0036]    In one version of the embodiment, the spring is selected from a group of springs that include a torsion spring or a compression spring. 
         [0037]    In one embodiment of the device, the return position is centered about an axis parallel to a major surface of the front cover and varies within a predetermined angular range. 
         [0038]    In one version of the embodiment, the predetermined angular range (ΔR) is about −8°≦ΔR≦+8°. 
         [0039]    In yet another aspect of the present invention, an electrical wiring device includes a housing having a front cover coupled to at least one body member, the front cover including a plurality of receptacle openings in a major front surface thereof. The plurality of receptacle openings is configured to receive a hot plug blade and a neutral plug blade of a corded electrical plug. The at least one body member includes at least one set of receptacle contacts including a hot receptacle contact and a neutral receptacle contact configured to mate with the hot plug blade and the neutral plug blade, respectively, when the corded electrical plug is inserted into the plurality of receptacle openings. A set of electrical terminations is accessible via at least one aperture in the housing, the at least one set of receptacle contacts being configured to receive electrical power from the at least a portion of the set of electrical terminations. A yoke structure is coupled to the front cover, the yoke structure includes a first railed bearing portion substantially disposed in parallel with a second railed bearing portion, the yoke structure defining a first portion and a translational portion. A shutter assembly includes a shutter element having a first indented opening and a second indented opening coupled to the first railed bearing portion and the second railed bearing portion respectively. The first indented opening includes a first substantially radial bearing interface and the second indented opening includes a second substantially radial bearing interface configured to ride the first railed bearing portion and the second railed bearing portion, respectively, from a return position to an open position in response to being engaged by the plurality of plug blades. The open position permits electrical engagement of the plurality of plug blades with the plurality of receptacle contacts. The yoke structure is configured to rotate the shutter element from the return position to a blocking position when disposed on the first portion in response to being engaged by an object via at least one of the plurality of receptacle openings to prevent the object from obtaining access to the at least one set of receptacle contacts. 
         [0040]    In one embodiment of the device, the shutter element includes a first major surface disposed on one side thereof and configured to be engaged by the plurality of plug blades, the shutter element further includes a second major surface disposed on a second side thereof, the first major surface being substantially parallel to the second major surface. 
         [0041]    In one embodiment of the device, the shutter element includes a first major surface configured to be engaged by the plurality of plug blades, the shutter element further includes a first lateral rib portion disposed at a first edge of the first major surface and a second lateral rib portion disposed at a second edge of the first major surface parallel to the first edge, the first lateral rib portion and the second lateral rib portion being configured to prevent the first major surface from abutting an interior major surface of the front cover when the shutter assembly is disposed in the return position. 
         [0042]    In one embodiment of the device, the each of the first railed bearing portion and the second railed bearing portion include a first portion extending from an interior major surface of the front cover in a substantially perpendicular direction to a pivot position, each of the first railed bearing portion and the second railed bearing portion further extending from the pivot position along the translational portion at a predetermined angle relative the first portion, wherein the shutter element is translated from the return position to the open position in a direction parallel to the interior major surface of the front cover a distance substantially equal to a width of one of the plurality of receptacle openings. 
         [0043]    In one version of the embodiment, the predetermined angle is greater than about thirty five degrees. 
         [0044]    In one embodiment of the device, the shutter element includes an aperture configured to allow one of the plurality of plug blades to pass through in the open position. 
         [0045]    In one embodiment of the device, the shutter element includes a seat portion configured to accommodate a spring, the spring being disposed between the seat portion and an anti-probing portion of the front cover. 
         [0046]    In one version of the embodiment, the spring is selected from a group of springs that include a torsion spring or a compression spring. 
         [0047]    In one embodiment of the device, the housing includes a wiring device housing, a duplex receptacle housing, a decorator housing, an extension cord housing, a multiple outlet strip housing, a combination receptacle and switch housing. 
         [0048]    In one embodiment the device further includes a protection circuit, a ground fault circuit interrupter, an arc fault circuit interrupter, or a surge protective device. 
         [0049]    In one embodiment of the device, the shutter element is configured to rotationally align with end portions of the plurality of plug blades in response to an asymmetry in respective lengths of the plurality of plug blades. 
         [0050]    Reference is made to U.S. Pat. No. 8,044,299, which is incorporated herein by reference as though fully set forth in its entirety, for a more detailed explanation of an electrical device being configured to accommodate a shutter assembly in the front cover thereof. To be specific, U.S. Pat. No. 8,044,299 discloses a GFCI electrical device, an AFCI electrical device, 15 A electrical device, 20 A electrical device, a GFCI/switch combination electrical device, GFCI/Night light combination electrical device, a TVSS electrical device, a power outlet strip electrical device, a portable electrical device, and a raceway electrical device, all of which are configured to accommodate a shutter assembly in the front cover thereof and all of which are incorporated herein by reference as though fully set forth in their entirety. 
         [0051]    Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings. 
         [0052]    It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein. It should also be appreciated that terminology explicitly employed herein that also may appear in any disclosure incorporated by reference should be accorded a meaning most consistent with the particular concepts disclosed herein. 
         [0053]    The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the invention and together with the description serve to explain the principles and operation of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0054]    In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. 
           [0055]      FIG. 1  is a perspective view of an electrical device with the front cover and the shutter assemblies removed in accordance with an embodiment of the present invention; 
           [0056]      FIG. 2  is a perspective view of an interior of the front cover and the shutter assemblies depicted in  FIG. 1 ; 
           [0057]      FIG. 3  is a perspective view of an interior of the front cover with the shutter assemblies installed in accordance with the present invention; 
           [0058]      FIGS. 4A-4B  are perspective views showing an underside and a topside, respectively, of the shutter element depicted in  FIG. 1 ; 
           [0059]      FIGS. 5A-5B  are detail views showing an interior of the front cover with an installed shutter assembly in a return position and in an open position, respectively, in accordance with the present invention; 
           [0060]      FIG. 6  is a cross sectional view of the shutter assembly in a return position in accordance with the present invention; 
           [0061]      FIG. 7A-7D  are cross sectional views of the shutter assembly in a hot blocking position or a neutral blocking position in accordance with the present invention; 
           [0062]      FIG. 8A-8C  are cross sectional views of the shutter assembly with a corded plug blade assembly driving the shutter element along a translational portion of the guide structure to the open position in accordance with the present invention; 
           [0063]      FIGS. 9A-9B  are cross sectional views of the shutter assembly with a corded plug blade assembly fully inserted and the shutter element in an open position; 
           [0064]      FIG. 10  is a perspective view of an electrical device with the front cover and the shutter assemblies removed in accordance with an alternative embodiment; 
           [0065]      FIG. 11  a perspective view of an interior of the front cover and the shutter assemblies depicted in  FIG. 10 ; 
           [0066]      FIGS. 12A-12B  are perspective views of an interior of the front cover with the shutter assemblies installed in accordance with the alternate embodiment depicted in  FIG. 10 ; 
           [0067]      FIGS. 13A-13B  are perspective views showing an underside and a topside, respectively, of the shutter element depicted in  FIG. 10 ; 
           [0068]      FIGS. 14A-14B  are detail views showing an interior of the front cover with an installed shutter assembly in a return position and in an open position, respectively, in accordance with the alternate embodiment depicted in  FIG. 10 ; 
           [0069]      FIG. 15  is a cross sectional view of the shutter assembly in a return position in accordance with the alternate alternative embodiment depicted in  FIG. 10 ; 
           [0070]      FIGS. 16 and 17  are cross sectional views of the shutter assembly in a “blocking” position in accordance with the alternate embodiment depicted in  FIG. 10 ; 
           [0071]      FIG. 18  is a cross sectional view of the shutter assembly with a corded plug blade assembly driving the shutter element along a translational portion of the guide structure to the open position in accordance with the alternate embodiment depicted in  FIG. 10 ; and 
           [0072]      FIG. 19  is a cross sectional view of the shutter assembly with a corded plug blade assembly fully inserted and the shutter element in an open position in accordance with the alternate embodiment depicted in  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION 
       [0073]    Reference will now be made in detail to the present exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. An exemplary embodiment of an electrical device with a shutter assembly of the present invention is shown in  FIG. 1 . Specifically, the electrical wiring device is designated generally throughout by reference numeral  10  or  10 ′, the shutter by reference numeral  20  or  20 ′, and the spring by reference numeral  30  or  30 ′. As described in further detail below, the shutter  20  or  20 ′ of the present invention features four shutter positions: three shutter positions (i.e., return, hot blocking and neutral blocking) correspond to the pivotal portion of the guide structure, and one shutter position (open) corresponds to a translational portion of the guide structure. 
         [0074]    With reference to  FIG. 1 , the proposed  15 A shutter design may be used in an electrical wiring device  10 , which is shown herein as a 15 A receptacle device. Obviously, the proposed shutter design may be adapted for use in protective wiring devices such as GFCIs, AFCIs, TVSSs and the like. Upon information and belief, the proposed shutter design may be adapted for use in other electrical wiring devices. 
         [0075]    Receptacle  10  includes a cover  12  and a back body  14 . The receptacle  10  is a duplex device and thus provides two sets of plug blade openings, one set at each end thereof. Each set of plug blade openings includes a ground prong aperture  12 - 1 , a hot opening  12 - 2  and a neutral opening  12 - 3 . The cover  12  is configured to mate with a back body  14  that includes a ground strap  14 - 1 , a hot conductor that includes hot contacts  14 - 2  and a neutral conductor that includes neutral contacts  14 - 3 . The ground aperture  12 - 1  is thus in communication with a ground contact  14 - 12  formed in the ground strap  14 - 1 , the hot aperture  12 - 2  is in communication with a hot contact  14 - 2  and the neutral aperture  12 - 3  is in contact with a neutral contact  14 - 3 . The shutter  20  is positioned between each set of hot and neutral plug blade openings ( 12 - 2 ,  12 - 3  respectively) and their corresponding hot and neutral contacts ( 14 - 2 ,  14 - 3 , respectively). Shutter  20  may also be employed in receptacle configurations in which a ground contact and aperture are omitted, referred to as a “two opening receptacle.” Each shutter  20  is equipped with a dual-torsion return spring  30  that is configured to move the shutter to a “return” position when no external force is applied to the shutter (either by corded plug blades or by a foreign object). 
         [0076]    In reference to  FIG. 2 , the two piece shutter assembly—including the shutters  20  and their corresponding return springs  30 —are shown prior to being inserted into the rear portion of the cover  12 . The shutter  20  is described in detail with reference to  FIGS. 4A and 4B  below. The dual torsion spring  30  includes retention portions  30 - 1  at each side thereof, the retention portions  30 - 1  are configured to be inserted into snap-in (“spring catch”) elements  12 - 22  formed in the anti-probing wall  12 - 20  (adjacent to the hot aperture  12 - 2 ) of cover  12 . The return spring  30  further comprises a central bearing portion  30 - 3  that is configured to engage the spring  30 ; the bearing portion  30 - 3  is disposed between each coiled spring element  30 - 2 . Upon information and belief, each coiled spring element  30 - 2  is approximately 0.1 inches in diameter and is fabricated from a wire that is 0.01 inches in diameter. The return spring  30  is configured to apply approximately 100-200 grams of rotational force to the shutter  20  in order to set the shutter  20  in the return position. 
         [0077]    The interior portion of the cover  12  includes a plurality of gussets (i.e., structural ribs)  12 - 7 ,  12 - 8 ,  12 - 9 ,  12 - 40  and  12 - 50  that are configured to provide the cover  12  with a certain amount of rigidity so that it resists bending and deformation due to twisting or torsional forces. Gusset  12 - 50  is also employed to electrically isolate the ground opening  12 - 1  from the hot and neutral conductors ( 14 - 2 ,  14 - 3 , not shown). In addition, gussets  12 - 40  and  12 - 50  are spaced apart to accommodate a shutter  20  therebetween. To be clear, the shutter  20  is not retained or confined between ribs  12 - 40  and  12 - 50  by frictional fit. As described in greater detail below, there is functional clearance between the gussets  12 - 40  and  12 - 50  that allows the shutter  20  to move side-to-side. The interior face of each gusset  12 - 40 ,  12 - 50  is used to support a guide rib  12 - 4 . Attached to each guide rib  12 - 4  and extending along substantially parallel to gusset  12 - 40 ,  12 - 50  is a shutter catch  12 - 5 . Extending substantially perpendicular from the each guide rib  12 - 4  and shutter catch  12 - 5  is a return rib  12 - 30 . The return rib  12 - 30  is formed on the interior major surface of front cover  12  as shown. The interior portion of the cover  12  also includes a plurality of stand-off elements  12 - 6 , anti-probing walls  12 - 10 , and  12 - 51 . 
         [0078]    The purpose and unique functionality of the guide rib  12 - 4 , shutter catch  12 - 5 , return rib  12 - 30 , stand-off elements  12 - 6 , and anti-probing walls  12 - 10 ,  12 - 20 , and  12 - 51 , are explained in further detail below with reference to  FIGS. 6-9B . This unique functionality is based on the unique structure, positioning of these elements within the interior portion of the cover  12 , and the relationship of these elements with the unique structural aspects of shutter  20 . 
         [0079]    Referring to  FIG. 3 , the two piece shutter assembly ( 20 ,  30 ) is shown disposed in the interior portion of the cover  12 . In this view, the guide ribs  12 - 4  are disposed within openings  20 - 4 ; each opening  20 - 4  is configured as an indented or recessed region formed in the side of the shutter. Moreover, the recessed openings  20 - 4  allow the shutter to move about the guide rails  12 - 4 ; i.e., no part of the shutter  20  mates with, or performs a snap-fit with the guide rails  12 - 4 , including catch detents  20 - 8 . The interior major surface  20 - 2 ′ of the hot blocking pad is suspended partially over the stand-off elements  12 - 6 . Similarly, the interior major surface  20 - 3 ′ of the neutral blocking pad is suspended partially over the shutter catches  12 - 5  and over return ribs  12 - 30  (not visible in this view). The return spring  30  applies a small force to the shutter  20  such that it is disposed in the return position. 
         [0080]    Referring now to  FIGS. 4A and 4B , isometric detail views of the shutter  20  are provided. The shutter  20  is fabricated by, e.g., injection molding a suitable plastic material such as Nylon, Polycarbonate, Acetal, Acrylic, Polyester, polyurethane, etc. 
         [0081]      FIG. 4A  shows the underside of the shutter  20 , i.e., the major surface that faces the interior of the device  10  when the shutter is installed within the cover  12 . In this view, the interior major surface  20 - 2 ′ of the hot blocking pad  20 - 2  is shown to the left of the opening  20 - 20  and the interior major surface  20 - 3 ′ of the neutral blocking pad  20 - 3  is shown to the right thereof. (Pads  20 - 2  and  20 - 3  are shown in  FIG. 4B ). Because the shutter  20  is a relatively thin structure (approximately 1/16 th  of an inch), gussets  20 - 5  are formed around a perimeter portion of the shutter  20  to provide strength and rigidity. The aperture  20 - 20  is disposed between the hot blocking pad  20 - 2  and the neutral blocking pad  20 - 3 , and is configured to allow a hot plug blade to pass through when the shutter  20  is in an open position. 
         [0082]    A lateral opening  20 - 4 , i.e., a recessed region or indentation, is formed in each side of shutter  20  to accommodate the guide ribs  12 - 4  therewithin. Specifically, the opening  20 - 4  provides a sufficient amount of clearance so that the shutter  20  can move freely about the guide rails  12 - 4  as it translates from the return position to the open position. Thus, during this translational movement, the bearing surfaces  20 - 9  make glancing or tangential contact with the guide ribs  12 - 4  so that the shutter  20  moves in two dimensions x, z about the guide rib  12 - 4 . ( FIG. 4B  shows the dimensional axes x, y, and z to represent the three dimensional operating space of the shutter  20 ). Moreover, a functional clearance is provided in the y-direction (Δy) between the lateral edges of the shutter  20  and the side walls  12 - 40  and  12 - 50 . (There is no friction fit or interference fit between the shutter edges and the walls  12 - 40 ,  12 - 50 ). Thus, when the shutter is translated in the x-z plane by a corded plug, or rotated in the x-z plane by an object, it is free to wobble in all three dimensions (Δx, Δy, Δz). This “give” or ability to float or wobble around the ribs  12 - 4  substantially prevents the shutter from becoming damaged, jammed or stuck after repeated usage. The shutter&#39;s ability to “float” enables the shutter to accommodate plug blades that are not perfectly parallel, bent or are not of equal length, or plug blade edges that are sharp (and can gouge and nick the shutter). In brief, the floating ability also allows the user to insert the plug at an angle without jamming or damaging the shutter. 
         [0083]      FIG. 4B  shows the topside of the shutter  20 , that is, the side that faces the cover  12  when the shutter is installed therein. The hot blocking pad  20 - 2  and the neutral blocking pad  20 - 3  are substantially flat planar surfaces, i.e., they are not inclined. The shutter  20  further includes interior gussets  20 - 11  that form a spring seat  20 - 30  for return spring  30 . Specifically, the spring seat  20 - 30  is configured to accommodate the central bearing portion  30 - 3  of spring  30 . However, the shutter  20  does not retain any portion of the spring  30 . In other words, the shutter  20  and the spring  30  do not form a module; they are only coupled together within the front cover  12 . Referring back to  FIG. 2 , the anti-probing wall  12 - 20  is disposed within the shutter aperture  20 - 20 ; when the shutter is installed in the cover  12 . However, the shutter  20  and the anti-probing wall  12 - 20  are not connected to each other. Finally, the topside of the shutter  20  includes gussets  20 - 6  and  20 - 7 ; these elements have the same function as the perimeter gussets  20 - 5  shown in  FIG. 4A  (i.e., they provide strength and rigidity to the shutter  20 ). 
         [0084]    Referring to  FIGS. 5A and 5B , in situ detail views of the underside of shutter  20  in the return position and in the open positions are shown.  FIG. 5A  includes a sectional line A-A; arrow A 1  indicates a first sectional viewpoint whereas arrow A 2  indicates the opposite sectional viewpoint. See  FIGS. 7-9 . 
         [0085]      FIG. 5A  shows the underside of the shutter  20  when it is in the return position and is a detail view of  FIG. 3 . In this view, the guide ribs  12 - 4  are disposed within the openings  20 - 4 . The interior major surface  20 - 2 ′ of the hot blocking pad is suspended partially over the stand-off elements  12 - 6 . Similarly, the interior major surface  20 - 3 ′ of the neutral blocking pad is suspended partially over the stand-off elements  12 - 5  and over the return ribs  12 - 30  (not visible in this view). The shutter spring  30  applies a small force to the shutter  20  toward the interior surface of the front cover  12  such that the shutter  20  is in the return position. 
         [0086]    In  FIG. 5B , the underside of the shutter  20  is shown in the open position. The force applied by the corded plug blades moves the shutter  20  to the left (in this view) so that the cover aperture  12 - 2  and the cover aperture  12 - 3  are misaligned with the shutter contact pads  20 - 2 ,  20 - 3 , respectively, to allow the corded plug blades to mate with contacts  14 - 2  and  14 - 3  (not shown). 
         [0087]    With reference to  FIGS. 6-9B , the shutter  20  may be in one of four shutter positions that correspond to one of two guide rail  12 - 4  portions. Specifically, the guide rail  12 - 4  includes a pivotal region  12 - 4 - 1  and a translational region  12 - 4 - 2 . When the shutter  20  is disposed in the pivotal region  12 - 4 - 1 , the shutter may be in the return position, a hot blocking position or a neutral blocking position. When the shutter  20  is disposed in the translational portion of the guide structure, the shutter is in or moving to the open position. 
         [0088]    Referring to  FIG. 6 , a cross-sectional view of an electrical wiring device  10  taken along section-A 1  ( FIG. 5A ) is shown, with the shutter  20  in the return position. During assembly, the spring  30  is installed to position the shutter  20  in the return position per a translational force “F” as shown. The return spring  30  applies approximately 100-200 grams of translational force to bias the shutter  20  against return ribs  12 - 30 . In this position, the anti-probing slot  20 - 54  is engaged with the anti-probing wall  12 - 51  and the far edge  20 - 53  of shutter contact pad  20 - 2  is engaged with stand-off element  12 - 6 . 
         [0089]    Referring to  FIGS. 7A, 7B, 7C and 7D , cross-sectional views of the electrical wiring device  10  are shown when a single foreign object is inserted into one of the cover apertures ( 12 - 2 ,  12 - 3 ).  FIGS. 7A and 7B  are cross-sectional views of an electrical wiring device  10  taken along “A 1 ” of the view illustrated in  5 A.  FIGS. 7C and 7D  are cross-sectional views of an electrical wiring device  10  taken along “A 2 ” of the view illustrated in  5 A. In these views, the shutter  20  is rotated from the return position into one of the blocking positions to defeat an object inserted into a single opening. 
         [0090]    For example,  FIG. 7A  shows an object being inserted into the hot aperture  12 - 2 , whereas  FIG. 7C  shows the opposite cross sectional view.  FIG. 7C  provides a better view of the pivotal region  12 - 4 - 1  and the translational region  12 - 4 - 2 . Note that the shutter bearing  20 - 9  (or any other part of the shutter) is not pinned to the guide rail  12 - 4  (or any other part of the cover  12 ); thus, it is free to move within the pivotal region  12 - 4 - 1  disposed between the shutter catch  12 - 5  and the bend in the guide rail. The translational region  12 - 4 - 2  is thus approximately within the range of positions between the bend in the guide rail and the bottom of the guide rail  12 - 4 . 
         [0091]    When an object is inserted into the hot aperture  12 - 2 , anti-probing wall  12 - 51  disengages from anti-probing slot  20 - 54  so that the far edge of  20 - 2  will disengage from stand-off elements  12 - 6 . After the shutter rotates from the return position and into the hot blocking position, the return ribs  12 - 30  engage with gussets  20 - 7  (see  FIG. 7A ). In  FIG. 7C , the shutter catches  12 - 5  are captured by the catch detents  20 - 8  formed in the neutral blocking surface  20 - 3 . In the hot blocking position therefore, the single object is prevented from engaging the hot receptacle contact  14 - 2  by the anti-probing wall  12 - 20  and the shutter&#39;s hot blocking surface  20 - 2 . 
         [0092]      FIG. 7B  shows an object being inserted into the neutral aperture  12 - 3 .  FIG. 7D  shows the opposite cross sectional view of the resulting functionality of the device&#39;s structure per an object&#39;s insertion into the neutral aperture  12 - 3 . When an object is inserted into the neutral aperture  12 - 3 , bearing surfaces  20 - 9  engage their respective bends in the guide ribs  12 - 4  (see  FIG. 7D ). Each guide rail bend forms a pivot point that allows the shutter  20  to rotate when the bearing surfaces  20 - 9  engage their respective pivots (i.e., guide rail bends). The shutter rotates until its anti-probing slot  20 - 54  engages the anti-probing wall  12 - 51  and the far edge of  20 - 2  engages stand-off elements  12 - 6  (see  FIG. 7B ). Thus, the single object is prevented from engaging the neutral receptacle contact  14 - 3  by the anti-probing wall  12 - 10  and the shutter&#39;s neutral blocking surface  20 - 3 . 
         [0093]    As described and illustrated in the foreign object probing scenarios provided above, when the bearing surface  20 - 9  engages the guide rail bend, the shutter  20  cannot translate any significant distance in the x-direction (no relative movement to the left or right in  FIGS. 7A-7D ). 
         [0094]    Note again that the pivot region  12 - 4 - 1  is so named because the bearings  20 - 9  may be displaced over this region, or range, simply because the bearing  20 - 9  is not fixed or pinned to the rail. There can be movement, therefore, of the shutter bearing  20 - 9  in the z-direction as it slides along the vertical portion of its respective guide rib  12 - 4  (between the return position and the guide rib bend in a blocking position). Stated differently, once the bearing surfaces  20 - 9  reach their respective guide rib bends, the shutter  20  stops moving in the z-direction and rotates into the blocking position. In one embodiment, the radiuses of the bearing surfaces  20 - 9  are substantially the same as the radiuses at the inside of each of the bends in the guide ribs  12 - 4 . 
         [0095]    In one embodiment, when a foreign object is inserted into either the hot receptacle aperture  12 - 2  or the neutral receptacle aperture  12 - 3  as described with respect to  FIGS. 7A-D  above, the object will strike blocking pad  20 - 2  or  20 - 3  and cause the shutter to rotate around the y-axis about 8° in one direction until the shutter is stopped in the manner described above. Thus, −8°≦ΔR≦+8°, wherein AR denotes the approximate rotational limits of the shutter. 
         [0096]    Referring to  FIGS. 8A-8C, and 9A-9B , cross-sectional views are shown of the electrical wiring device  10  in the open position.  FIGS. 8A and 9A  are cross-sectional views of an electrical wiring device  10  taken along “A 1 ” of the view illustrated in  5 A.  FIGS. 8B, 8C and 9B  are cross-sectional views of an electrical wiring device  10  taken along “A 2 ” of the view illustrated in  5 A. As illustrated in these views, the shutter  20  is shown in various positions as it traverses the translational region  12 - 4 - 2  (i.e., the x and z movement from a return position to the open position). 
         [0097]    In reference to  FIG. 8A  and  FIG. 8B , a preliminary “unlocking” position is shown wherein the insertion of the corded plug blades has just begun; i.e., the shutter  20  has been moved by only a small distance. Specifically, when corded plug blades are inserted into apertures  12 - 2 ,  12 - 3  and overcome the force of the return spring  30 , the shutter  20  starts to move in the x and z directions (guided by guide ribs  12 - 4 ) so that the gussets  20 - 7 , catches  12 - 5 , anti-probing wall  12 - 51 , and the far edge of  20 - 3  separates from the return ribs  12 - 30 , catch detents  20 - 8 , anti-probing slot  20 - 54 , and the stand-off elements  12 - 6 , respectively. Moreover, the bearings  20 - 9  are directed down the vertical portion of the guide rails, through the guide rail bends and down the translational portion  12 - 4 - 2  of the guide ribs  12 - 4 . Once this occurs, the shutter  20  opens and allows the corded plug blades to engage the respective contacts  14 - 2 ,  14 - 3 . When the plug blades are removed, the return spring  30  is structured and configured to reverse the above described movement until the shutter  20  is returned to the return position as shown and described with respect to  FIG. 6 . 
         [0098]    In reference to  FIG. 8C , a cross-sectional view of an electrical wiring device  10  showing the shutter  20  in the translational region  12 - 4 - 2  (described above) is disclosed. Again, as the hot and neutral blades press shutter  20  downwardly, the shutter  20  may remain substantially parallel to the front cover while it moves generally to the left in the x-direction. In this view, the width (ΔW) of the opening  20 - 4  is seen to be much greater than the thickness of the guide rib  12 - 4 . Again, this clearance allows the shutter  20  to wobble, or move back and forth about the guide rib  12 - 4  as it traverses the translational region  12 - 4 - 2 . 
         [0099]    In conventional shutter mechanism designs, the assumption is that the keyed receptacle openings force the plug blades to be inserted into the receptacle openings simultaneously. While this is true to a certain extent, there is still a great deal of room for skewing and side-to-side movement until the blades are captured by the receptacle contacts. For example, when a person attempts to insert a corded plug into a receptacle opening, he/she very often wiggles the plug in an effort to align the plug blades with the cover apertures. These back and forth skewing movements cause the plug blades to strike the shutter with varying amounts of force at different instants of time (not simultaneously). Similar issues can be caused by plug blades that are bent or not of the same length. Conventional shutters typically employ a linear slide motion and become jammed and inoperative after they absorb repeated nicks and gouges. The present invention seeks to address this issue by allowing the shutter  20  to freely float in the return position and as it traverses the various portions/regions of the guide rail  12 - 4 . Accordingly, the counter-intuitive wobbling motion prevents damage to the shutter during plug insertion. 
         [0100]      FIGS. 9A-9B  are cross sectional views of the shutter  20  in an open position with corded plug blades fully inserted. In this view, the return spring  30  is in compression within the device  10  and the bearing surface  20 - 9  is shown at a bottom potion of the translational region  12 - 4 - 2  on the guide rib  12 - 4 . 
         [0101]    Turning to the embodiment of  FIGS. 10-19 , an alternative spring (compression spring  30 ′) and shutter  20 ′ arrangement is disclosed. This embodiment also includes a guide rail  12 - 4  that features a pivotal region  12 - 4 - 1  and a translational region  12 - 4 - 2 . When the shutter  20  is disposed in the pivotal region  12 - 4 - 1 , the shutter may be in the return position, a hot blocking position or a neutral blocking position. When the shutter  20  is disposed in the translational portion  12 - 4 - 2  of the guide rail  12 - 4 , the shutter is in, or moving to, the open position. As before, the pivot region  12 - 4 - 1  is so named because the bearings  20 - 9  may slide over this region during movements between the return position and one of the blocking positions. Again, this movement occurs or can occur because the bearing  20 - 9  is not fixed or pinned to the rail. There can be movement, therefore, of the shutter bearing  20 - 9  in the z-direction as it slides along the vertical portion of its respective guide rib  12 - 4  (between the return position and the guide rib bend in a blocking position). Once the bearing  20 - 9  engages the bend in the guide rail  12 - 4 , the movement stops and the shutter rotates into a blocking position. 
         [0102]    Referring to  FIG. 10 , a perspective view of an electrical device  10 ′ with a front cover  12 ′ and the shutter assemblies removed is shown in accordance with an alternative embodiment.  FIG. 10  is similar to  FIG. 1 . One difference between  FIG. 10  and  FIG. 1  is the use of dual compression springs  30 ′ instead of the dual torsion springs  30  (as shown in  FIG. 1 ). The compression springs  30 ′ and the torsion springs  30  are configured to apply different kinds of forces and thus operate the shutters differently. The modified shutters  20 ′ are described in further detail below with respect to  FIGS. 13A and 13B . 
         [0103]    In reference to  FIG. 11 , the two piece alternative shutter assembly—including the shutters  20 ′ and their corresponding compression springs  30 ′—are shown prior to being inserted into the rear portion of the cover  12 ′.  FIG. 11  is similar to  FIG. 2 ; however, there are some differences. In addition to showing the alternative shutter assembly, this embodiment does not include the snap-in (“spring catch”) elements  12 - 22  of cover  12  that are shown in  FIG. 2 . The snap-in elements  12 - 22  are helpful in maintaining the retention portions  30 - 1  of the torsion springs  30  in a static position. However, such snap-in elements  12 - 22  are not necessary with the use of compression springs  30 ′. As such, this alternative embodiment can save on manufacturing costs (i.e., the step of forming the snap-in elements  12 - 22  can be avoided). As before, the shutter  20  and the spring  30  do not form a module (i.e., they do not form a unit that can be installed in the cover  12 ). They are installed in the cover separately. 
         [0104]    Referring to  FIGS. 12A and 12B , the two piece alternative shutter assembly ( 20 ′,  30 ′) is shown coupled to the interior portion of the cover  12 ′.  FIGS. 12A and 12B  are similar to  FIG. 3  with some differences. More specifically,  FIG. 12A  shows the shutters  20  in a return position (where the compression springs  30  apply a small force to the shutters  20  to maintain the shutters  20  in the “return” position). When a foreign object (e.g., a “bobby pin”) is inserted into either the hot or the neutral position, the shutter is rotated into a blocking position so that the object cannot access the set of hot and neutral plug blade openings ( 12 - 2  and  12 - 3 , respectively). 
         [0105]    Thus, the shutter assembly of the present invention features four shutter positions (return, blocking (hot and neutral) and open) that correspond to two guide rail regions (pivotal region  12 - 4 - 1  and translational region  12 - 4 - 2 ). 
         [0106]      FIG. 12B  shows the shutters  20 ′ in an “open” position (where a corded plug (not shown) has been inserted to actuate the shutters  20 ′ to such a position in a similar manner as described above with respect to shutters  20 ). 
         [0107]    Turning to  FIGS. 13A and 13B , isometric detail views of the shutter  20 ′ are provided.  FIGS. 13A and 13B  are similar to  FIGS. 4A and 4B , respectively, with some differences.  FIGS. 13A and 13B  do not include an interior gusset  20 - 11  as shown in  FIGS. 4A and 4B . Instead,  FIGS. 13A and 13B  include a spring mount  20 - 30 ′ that is configured to accommodate one end of compression spring  30 ′ (i.e., spring mount  20 - 30 ′ is configured to fit within the diameter of an end of the compression spring  30 ′ when the compression spring  30 ′ is placed within the opening  20 - 20  of the shutter  20 ′ to create the two piece shutter assembly ( 20 ′,  30 ′)). 
         [0108]    Referring to  FIGS. 14A and 14B , in situ detail views of the underside of shutter  20 ′ in the return and in open positions, respectively, are shown.  FIGS. 14A and 14B  are similar to  FIGS. 5A and 5B , respectively, with the same previously described differences. As shown in  FIG. 14A , the compression spring  30 ′ applies a small force to the shutter  20 ′ in the x-direction (to the right) such that the shutter  20 ′ is in the return position (as opposed to applying a small force to the shutter  20  toward the interior surface of the front cover  12 , as shown and described with respect to  FIG. 5A ). 
         [0109]    Turning to  FIG. 15 , a cross-sectional view of an electrical wiring device  10 ′ taken along section A ( FIG. 14A ) is shown, with the shutter  20 ′ in the return position. The embodiment shown in  FIG. 15  is similar to the embodiment shown in  FIG. 6 , with some differences. During assembly, the spring  20 ′ is employed to position the shutter  20 ′ in the return position per a translational force “F” of approximately 100-200 grams. In particular, the spring  30 ′ applies a force in the x-direction (to the left) to maintain the shutter  20 ′ in the return position. The direction of the force being applied by the compression spring  30 ′ is different than the direction of the force being applied by the torsion spring  30  (which applies a translational force in the z-direction (up), as shown and described with respect to  FIG. 6 ). 
         [0110]    Another difference between the embodiment of  FIG. 6  and the embodiment of  FIG. 15  relates to the shutter&#39;s disposition in the return position. As shown in  FIGS. 4A-4B , the shutter element  20  is shown to include lateral rib portions ( 20 - 6 ,  20 - 7 ) that are on either side of the shutter major surface ( 20 - 2 ,  20 - 3 ). In  FIG. 6 , the lateral ribs ( 20 - 6 ,  20 - 7 ) prevent the blocking surfaces ( 20 - 2 ,  20 - 3 ) from abutting the interior surface of the front cover  12  when the shutter assembly is disposed in the return position. In other words, the rib portions function as stand-offs in the return position. In the embodiment of  FIG. 15 , no part of the shutter  20  touches the interior surface of the front cover  12 . Instead, the actual position of shutter  20  is substantially random in the return position, in that it can be and move within an approximate range of +/−8° about a plane parallel to the front cover in the return position. Stated in another way, if one were to insert a foreign object into aperture  12 - 3 , for example, the shutter would rotate. As the foreign object is inserted further, the shutter would continue to rotate until it reaches the blocking position; at that point, the shutter  20  would stop rotating. Thus, the return position is separate and distinct from the blocking positions. 
         [0111]    Referring to  FIGS. 16 and 17 , cross sectional views of the electrical wiring device  10 ′ taken along sectional A ( FIG. 14A ) are shown.  FIGS. 16 and 17  illustrate the functionality of the shutter  20 ′, spring  30 ′ and cover  12 ′ when a single foreign object is inserted into only one of the cover apertures  12 - 2 ,  12 - 3  and exerts an external force “F′” on shutter  20 ′. In these views, the shutter  20 ′ is rotated into a “blocking” position preventing a single foreign object from engaging the hot receptacle contact  14 - 2  ( FIG. 16 ) and the neutral receptacle contact  14 - 3  ( FIG. 17 ).  FIGS. 16 and 17  are similar to  FIGS. 7A and 7B , respectively, with the same previously described structural differences. As described with respect with  FIGS. 7A and 7B  (among other similar functionalities), there is no significant movement of the shutter  20 ′ in the x-direction (no relative movement to the left or right) in  FIGS. 16 and 17 . 
         [0112]    Turning to  FIG. 18 , a cross section view of the electrical wiring device  10 ′ taken along “A 1 ” of the view illustrated in  FIG. 14A  is shown.  FIG. 18  is similar to  FIG. 8A , and illustrates the functionality of the shutter  20 ′, spring  30 ′ and cover  12 ′ when corded plug blades are inserted into the cover apertures  12 - 2 ,  12 - 3  and exert an external force “F′” overcoming the force “F” exerted by compression spring  30 ′. In this view, the shutter  20 ′ is shown at the beginning (preliminary “unlocking” position) of its x and z direction movement (from a return position toward an eventual corded plug blade fully deployed/actuated position shown in  FIG. 19 ) guided by guide ribs  12 - 4  to the shutter&#39;s  20 ′ final full corded plug actuation position, which exposes hot contact  14 - 2  or neutral contact  14 - 3  for contact with the corded plug. If the corded plug blades are removed, the compression spring  30 ′ is structured and configured to move (via force F in the x-direction—to the left) the shutter  20 ′ back to the return position as shown and described with respect to  FIG. 15 . 
         [0113]    Referring to  FIG. 19 , a cross section view of the electrical wiring device  10 ′ taken along “A 1 ” of the view illustrated in  FIG. 14A  is shown.  FIG. 19  is similar to  FIG. 9A , and shows a corded plug blade in a fully deployed/actuated position with the hot blade “H” and the neutral blade “N” of the corded plug making contact with the hot contact  14 - 2  and neutral contact  14 - 3 , respectively. The movement of the plug blades causes the shutter  20 ′ to move down the guide ramp  12 - 4  (as described above) and compress the compression spring  30 ′ to its full compressed position within the device  10 ′. Once the corded plug blade is removed, the compression spring  30 ′ force F allows the shutter  20 ′ to move up along the guide ramp  12 - 4  and back to the return position as shown and described with respect to  FIG. 15 . 
         [0114]    Accordingly, when a corded plug is inserted into the cover apertures  12 - 2 ,  12 - 3 , the applied forces are more than enough to overcome the spring force of compression spring  30 ′, as discussed above. As described with other embodiments herein, this alternative embodiment allows for a side-to-side translation of the shutter in the x-z plane to the open position. 
         [0115]    While several inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. There is no intention to limit the invention to the specific form or forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention, as defined in the appended claims. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto; inventive embodiments may be practiced otherwise than as specifically described and claimed. 
         [0116]    All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
         [0117]    All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms. 
         [0118]    The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. 
         [0119]    As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and/or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc. 
         [0120]    It should also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited. 
         [0121]    Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about” and “substantially”, are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged; such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. 
         [0122]    The recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. 
         [0123]    All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate embodiments of the invention and does not impose a limitation on the scope of the invention unless otherwise claimed. 
         [0124]    No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
         [0125]    In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of” shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.