Abstract:
A sign is combined with an electrical outlet plate which can mount near or to existing electrical infrastructure to provide information such as direction toward an exit. A protruding and/or outwardly visible surface of the sign may be painted or adorned with a sign appliqué, and can be illuminated and/or photoluminescent to provide maximum visibility with or without electrical power. Advantageously, the sign can be mounted at electrical outlets and/or electrical switches that are near the floor and away from the ceiling, such that the sign remains visible even when lines of sight within a building are impaired, such as from smoke. In one exemplary embodiment, the sign is integrated into a portion of a standard-sized duplex cover plate, which can be mounted to an existing electrical junction box to preserve the functionality of adjacent electrical outlets or switches.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under Title 35, U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No. 61/504,473 filed Jul. 5, 2011 and entitled ELECTRICAL OUTLET COVER PLATE WITH SIGNAGE FEATURE, the entire disclosure of which is hereby expressly incorporated by reference herein. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to electrical outlet cover plates and signs and, more particularly, to illuminated signs combined with electrical cover plates. 
     2. Description of the Related Art 
     Exit signs mounted in buildings near ceilings and above doors are commonly found in businesses and public spaces, and are often required by law. These signs are designed to aid in egress from a building during emergencies, such as a fire. 
     While exit signs installed near ceilings and/or above doorways are suitable for some purposes, such signs may become obscured by smoke in a fire at even short distances, such as about 10 steps. When such signs are obscured in this way, building occupants may be unable to find guidance for quickly and efficiently reaching emergency exits, at precisely the time such guidance is needed most. 
     Further, structure fires or other emergencies may interrupt electrical power to the existing exit signs in a building. For interior areas with limited natural light, or which have smoke or other obstructions obscuring the exit signs, a loss of electrical power to lighted exit signs may render such signs difficult or impossible to see, again hinder building occupants from finding guidance when needed most. 
     A system of signage that provides reliable information to visitors in numerous and varied locations is desirable. For example, exit information in public structures is ideally visible from any location in a building, even when lines of sight are impaired and electrical power is not available, to safely guide visitors toward the building exits. 
     SUMMARY 
     The present disclosure provides a sign, in combination with an electrical outlet plate, which can mount near or to existing electrical infrastructure to provide information such as direction toward an exit. A protruding and/or outwardly visible surface of the sign may be painted or adorned with a sign appliqué, and can be illuminated and/or photoluminescent to provide maximum visibility with or without electrical power. Advantageously, the sign can be mounted at electrical outlets and/or electrical switches that are near the floor and away from the ceiling, such that the sign remains visible even when lines of sight within a building are impaired, such as from smoke. In one exemplary embodiment, the sign is integrated into a portion of a standard-sized duplex cover plate, which can be mounted to an existing electrical junction box to preserve the functionality of adjacent electrical outlets or switches. 
     In one form thereof, the present disclosure provides a sign, comprising: a cover plate adapted to be mounted to a wall near an electrical source, the cover plate having a wall mounting surface, an opposed outwardly facing plate surface, and a sign aperture extending from the wall mounting surface to the outwardly facing plate surface; and a lens received in the sign aperture and protruding outwardly therefrom such that an outwardly facing lens surface is spaced outwardly from the outwardly facing plate surface, the lens having a visual indicia disposed on the outwardly facing lens surface, the lens comprising at least one of: i) a photoluminescent material capable of absorbing photons and discharging the absorbed photons over a period of at least 10 minutes, and ii) a radioluminescent material. 
     In another form thereof, the present disclosure provides a sign, comprising: an electrical cover plate having a wall mounting surface, an opposed outwardly facing plate surface, and a sign aperture extending from the wall mounting surface to the outwardly facing plate surface; a lens received in the sign aperture and protruding outwardly therefrom such that an outwardly facing lens surface is spaced outwardly from the outwardly facing plate surface, the lens defining an interior cavity opposed to the outwardly facing lens surface, the lens comprising at least one of: i) a photoluminescent material capable of absorbing photons and discharging the absorbed photons over a period of at least 10 minutes, and ii) a radioluminescent material; and a light source operable to provide light to the lens, the light source disposed within the interior cavity. 
     In yet another form thereof, the present disclosure provides a method of installing a sign, the method comprising: removing an existing cover plate from an underlying electrical access point disposed at an interior wall of a building; removing an electrical apparatus from one of the existing cover plate and the underlying electrical access point, the step of removing an electrical apparatus creating an available space behind a cover plate aperture when the cover plate is mounted to the electrical access point; installing a lens over the cover plate aperture such that the lens faces outwardly through the cover plate aperture and away from a wall-contacting surface of the cover plate, and such that the lens at least partially occupies the available space behind the cover plate aperture; the lens comprising at least one of: i) a photoluminescent material capable of absorbing photons and discharging the absorbed photons over a period of at least 10 minutes, and ii) a radioluminescent material; and reattaching the existing cover plate to the underlying electrical access point. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above mentioned and other features and objects of this disclosure, and the manner of attaining them, will become more apparent and the disclosure itself will be better understood by reference to the following description of embodiments of the disclosure taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1A  is a perspective view of a sign and duplex cover plate combination made in accordance with the present disclosure; 
         FIG. 1B  is a front elevation view of a sign and duplex cover plate combination shown in  FIG. 1A ; 
         FIG. 2  is an exploded view of the sign and cover plate shown in  FIG. 1 , illustrating an arrangement of light sources inside the outwardly extending sign module; 
         FIG. 3A  is a bottom plan view of the lens of the sign module shown in  FIG. 2 ; 
         FIG. 3B  is a side elevation view of the lens of the sign module shown in  FIG. 2 ; 
         FIG. 3C  is a cross-sectional view of the lens of the sign module shown in  FIG. 2 , taken through line  3 C- 3 C of  FIG. 1A ; 
         FIG. 4A  is a perspective view of another sign and cover plate made in accordance with the present disclosure, in which two signs are combined with a switch plate; 
         FIG. 4B  is an elevation view of further cover plates usable with signs made in accordance with the present disclosure, and 
         FIG. 5  is a perspective, exploded view of a sign and duplex cover plate combination in accordance with the present disclosure. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. Although the exemplifications set out herein illustrate an embodiment of the disclosure, the embodiment disclosed below is not intended to be exhaustive or to be construed as limiting the scope of the disclosure to the precise form disclosed. 
     DETAILED DESCRIPTION 
     A photoluminescent sign is sized for mounting to standard electrical outlet covers. The cover may be mounted to a low point on a wall at a point of existing electrical infrastructure, such that the cover is disposed at eye level for a person crawling or low-walking out of a smoky building. The sign may have at least one indicia or message imprinted thereon, such as “EXIT” with an arrow pointing toward the direction of a nearby building exit. Other messages may be provided, such as “nearest fire extinguisher,” “non smoking room,” “turn lights off” or any other pertinent information. The sign may or may not be illuminated from within by a light source. The sign may also be mounted to any standard electrical cover plate, such as a standard duplex outlet cover plate or a light switch cover plate. 
     For purposes of the present disclosure, “photoluminescence” refers to the absorption and re-radiation of photons from a material. In the context of the lenses disclosed herein, such as lens  30 , the photoluminescent material does not immediately re-emit the radiation it absorbs, but instead emits such radiation over a period of at least several minutes. Photoluminescence materials includes phosphor materials, which are materials made of or containing a substance that exhibit the phenomenon of luminescence. For purposes of the present disclosure, phosphor materials are those materials which exhibit a slow decay in brightness after being “charged” with photons from a light source, such as over a period of at least several minutes. 
     Referring now to  FIGS. 1A, 1B and 3 , there is shown an exemplary embodiment of the present disclosure including sign assembly  10  combined with duplex cover plate  12 . A pair of insulated conductors  60 ,  70  extends from the rear of sign assembly  10 , with each conductor  60 ,  70  adapted to be connected to an electrical source. Next to sign assembly  10  on cover plate  12  are apparatus apertures  40 , which are sized to accept standard, wall mounted duplex electrical outlets  24  ( FIG. 5 ). Although apertures  40  are shown as having an appropriate size and shape for 120V duplex wall outlets commonly found in U.S. residences and businesses, it is contemplated that apertures  40  may have any shape and size to accommodate any electrical apparatus. Exemplary alternative cutouts may be sized and shaped for 220V wall outlets, or for light switches (as shown in  FIG. 4A  and described below), or any other wall-mounted electrical apparatus. 
     In an exemplary embodiment, duplex cover plate  12  is a standard duplex cover plate that is widely commercially available. For example, in the United States duplex cover plate  12  may be 4 13/16 wide×4⅞ tall, which is a standard “two-device” size cover plate which accommodates side-by-side left and right electrical devices (i.e., switches, outlets, etc.) arranged along the horizontal, 4 13/16 wide edges of plate  12 . 
     In the illustrative embodiment of  FIG. 2 , one of the two device apertures of duplex cover plate  12  is sign aperture  50 , which is sized and shaped to fit sign assembly  10  therewithin such that lens  30  of sign assembly  10  protrudes outwardly from outwardly-facing surface  26  (as best seen in  FIGS. 1A and 3A ). In the exemplary embodiment shown, lens  30  has a generally box-shaped outer profile, such that outwardly facing lens surface  32  includes five surfaces (top, bottom, sides and front) which are visible when lens  30  is mounted to cover plate  12 . However, it is contemplated that outwardly facing lens surface  32  may take other forms, such as a rounded or bulbous shape for example, which are capable of protruding outwardly past outwardly facing surface  26  of cover plate  12 . 
     As best seen in  FIGS. 3A-3C , lens  30  includes shoulder  38  formed at the base of lens  30 . Shoulder  38  protrudes laterally outwardly from the side edges of outwardly facing lens surface  32  such that when lens  30  is received in sign aperture  50 , shoulder  38  abuts the adjacent undersurface of cover plate  12 . More particularly, assembly of lens  30  to cover plate  12  is accomplished by passing lens  30  through aperture  50  from the back of plate  12  (i.e., from wall-contacting surface  28  toward outwardly facing surface  26 ). When fully received therein, lens  30  defines an outward protrusion distance P ( FIG. 3A ) such that outwardly facing lens surface  32  is spaced outwardly away from outwardly facing plate surface  26 . Advantageously, this outward spacing renders the side surfaces of outwardly facing lens surface  32  visible not only when looking directly at lens  30 , but also when looking at lens  30  from either side. In an emergency situation, such as a structure fire, a viewer will be able to see a series of sign assemblies  10 , both near and fat, because lens  30  protrudes outwardly. In an exemplary embodiment, distance P may be as little as 0.13 inches, 0.2 inches or 0.25 inches, or may be as much as 0.5 inches, 0.75 inches, 1, inch, or greater, or may be any distance within any range defined by any of the foregoing values. In one particularly exemplary embodiment, protrusion distance P may be 7/16 inches, which is large enough for lens  30  to be highly visible from all sides but small enough for lens  30  to avoid any undue interference with adjacent switches or electrical apparatus. 
     Alternatively, lens  30  may omit shoulder  38  such that assembly of lens  30  to cover plate  12  can occur along a front-to-back path, i.e., from outwardly facing plate surface  26  toward wall-contacting plate surface  28 . In this alternative embodiment, lens  30  may be press-fit into aperture  50  to provide initial fixation to cover plate  12 , and additional fixation may be provided by adhesive, for example. 
     In an exemplary embodiment, aperture  50  is between 1.25 to 1.3 inches wide and between 2.6 to 2.63 inches high, while width dimension W and height dimension H of lens  30  ( FIGS. 3B and 3C ) are slightly smaller than aperture  50 , such as about 1/32 inch or 1/16 inch smaller. Advantageously, these dimensions of sign aperture  50  are of common manufacture for so called “Decora” panel-type wall switches available from Leviton Manufacturing Company, Inc., or for standard ground-fault circuit interrupter (GFCI) devices commonly available. Thus, the standard outer dimensions of lens  30  allowing sign assembly  10  to be assembled to existing, inexpensive cover plates. 
     In one alternative, lens  30  can be made larger, either by expanding the size of aperture  50  or by expanding outwardly facing lens surface  32  past aperture  50 , e.g., by widening and/or lengthening the cross-section of lens  30  as surface  32  extends outwardly away from outwardly facing plate surface  26 . In this alternative embodiment, lens  30  would be arranged to assembly to cover plate  12  along the “front-to-back” assembly path described above. In yet another alternative, lens  30  can occupy the entire area of cover plate  12  entirely, such as by being integrally and/or monolithically formed with cover plate  12 . Moreover, it is contemplated that lens  30  can take any size and shape as required or desired for a particular application, including sizes large enough to cover the entire outwardly facing plate surface  26  or even to extend laterally past such surface. Regardless of the size and configuration of lens  30 , lens  30  may attach to cover plate  12  for mounting to a wall as described herein. 
     In the illustrated embodiment of  FIG. 3A , lens  30  is substantially hollow such that an inwardly facing lens surface  34  defines an interior cavity  36  open to wall mounting surface  28  of cover plate  12 . As best seen in  FIG. 2 , sign assembly  10  includes backing plate  22  disposed behind lens  30 , such that one side of backing plate  22  faces into interior cavity  36 . When backing plate  22  is coupled to lens  30  and cover plate  12  (as shown in  FIGS. 2 and 3A , and described further below), interior cavity  36  extends between wall-mounting surface  28  of cover plate  12  and inwardly facing lens surface  34  of lens  30 . In this configuration, interior cavity  36  is bounded at the front and sides by inwardly facing surface  34  and at the back by backing plate  22 . 
     Backing plate  22  includes upper and lower threaded holes  42 ,  44  for attachment of backing plate  22  to cover plate  12 . In an exemplary embodiment, threaded holes  42 ,  44  are provided by threaded anchors fixed to backing plate  22 . The threaded anchors may be made of a strong, resilient material such as aluminum or steel, such that backing plate  22  itself may be made from a softer material, such as a plastic or polymer. Backing plate  22  is attached to cover plate  12  by passing mounting screws  16 ,  18  through upper and lower mounting holes  46 ,  48  formed in cover plate  12 , then threading screws  16 ,  18  into upper and lower threaded holes  42 ,  44  of backing plate  22 . When screws  16 ,  18  are tightened, lens  30  (and, more particularly, shoulders  38 ) is trapped between backing plate  22  and the adjacent portion of wall-contacting surface  28  of cover plate  12 . In one exemplary embodiment, screws  16 ,  18  are spaced vertically from one another by 3 13/16 inches, such that their location is compatible with the standard screw holes found on many U.S. electrical outlet boxes. 
     In order to ensure and maintain proper alignment between lens  30  and backing plate  22  during assembly and use of sign assembly  10 , lens  30  may include alignment pins  52  ( FIGS. 2 and 3B ) which are received within pin holes  54  formed in backing plate  22 . In order to facilitate passage of conductors  60 . 70  out of interior cavity  36  of lens  30 , wire cutouts  56  may be formed in the back face of lens  30  as shown in  FIGS. 3B and 3C . In one alternative embodiment, backing plate  22  may be omitted from sign assembly  10 , and alignment pins  52  may then serve as standoffs to hold lens  30  away from the adjacent wall or other mounting surface. In this alternative embodiment, wire cutouts  56  can be omitted. 
     Referring now to  FIG. 2 , sign assembly  10 , a plurality of light sources  13  are shown mounted on backing plate  22 . In this illustrative embodiment, backing plate  22  is a printed circuit board which receives electrical power from insulated conductors  60 ,  70  and distributes this electrical power in a correct polarity and voltage to light sources  13 , such that application of power activates light sources  13 . In an exemplary embodiment, backing plate/circuit board  22  is made of a fiberglass material and imprinted with conductors. However, it is contemplated that the backing plate/circuit board  22  may be made from any material providing adequate rigidity and electrical insulation, and may be made of a material amenable to receiving imprinted conductors. 
     When light sources  13  are activated, light is provided within interior cavity  36  of defined by lens  30  as shown in  FIG. 3 . In this lighted embodiment, the material of lens  30  is translucent, which allows light from light source(s)  13  to pass therethrough to illuminate the part of lens  30  non-covered by appliqué  20  as described below. In the illustrative embodiment, lens  30  is constructed of a photoluminescent and translucent plastic. However, lens  30  may be made of any material that allows light to pass therethrough and/or is luminescent. 
     In one exemplary embodiment, lens  30  of sign assembly  10  is made of photoluminescent material, such that sign assembly  10  will remain “glowing” for a time even after power to light sources  13  is interrupted. Moreover, the illumination of light sources  13  provides ultraviolet energy to activate the photoluminescent material of lens  30 , thereby ensuring that lens  30  will glow brightly for a significant time span after power is lost. For example, the material of lens  30  may be polycarbonate or ABS plastic, which is robust and fire retardant. This material may be embedded with a phosphor, such as strontium aluminate activated with a suitable dopant (e.g. europium) to provide a photoluminescent quality to lens  30 . When so embedded, such phosphor materials exhibit substantial photon discharge over periods of time on the order of minutes or hours, such as at least 10 minutes. 
     In order to ensure a length and brightness of discharge for use in the context of building safety signs, an exemplary embodiment of the present disclosure provides lens  30  with a substantial material thickness T, as shown in  FIG. 3A . Such thickness provides a large volume of material for storage of photon energy by the embedded phosphor. In addition to the additional brightness and length of photon discharge provided by this large volume, additional enhancement is generated as the inner volume (i.e., the material at and near inwardly facing lens surface  34 ) discharges photons toward the outer volume (i.e., material at and near outwardly facing lens surface  32 ). These outwardly discharging photons are temporarily stored and re-emitted from the material, thereby serving to simultaneously discharge and “recharge” the photoluminescent material of lens  30 . 
     In an exemplary embodiment, thickness T is at least 0.10 inches, such as about ⅛-inch. It is contemplated that thickness T may be as little as 0.05 inches, 0.08 inches, 0.10 inches, or as much as 0.12 inches, 0.15 inches, 0.25 inches or more, or may be any thickness within any range defined by any of the foregoing values. Advantageously, lens  30  made in accordance with the present disclosure provides photon discharge sufficient to illuminate the material of lens  30  for at least 5 hours, and up to 24-32 hours. This timeframe provides ample time for egress of building occupants during an emergency where sign assembly  10  is used along walls in hallways or rooms. 
     Moreover, exemplary embodiments providing longer discharge times on the order of 24-32 hours can illuminate lens  30  even if the “charging” lights (which may include ambient natural light, ambient electrical light, or light from light source  13  for example) have not been available for an extended period of time before an emergency. In one example, a building&#39;s lights and electrical power may be shut off for the evening and restarted in the morning. Also during the evening time, ambient light from the sun will not be available to “charge” the material of lens  30 . The elapsed time of no “charging” may be, for example, about 12 hours. If an emergency occurs shortly after occupants have returned to the building the following morning, lens  30  is still able to illuminate the shortest path to an exit, for example, because the total discharge time is only about half elapsed. Thus, even without any significant recent “recharging” from ambient lights or light source  13 , sign assembly  10  is still able to provide its function of providing information in case of emergency. 
     The wavelength of light discharged from lens  30  depends on the internal crystal structure of the material. Colors provided in accordance with the present disclosure include aqua having a wavelength of about 490 nm, blue-green with a wavelength of about 505 nm, and green with a wavelength of about 520 nm. Green is provides the brightest discharge, while aqua provides the longest lasting discharge. However, it is contemplated that other colors may be provided having wavelengths as short as 200 nm and as long as 520 nm or greater, thereby discharging other colors such as pink. 
     In addition, it is contemplated that other phosphors may be used, including zinc sulfate compounds and Cadmium Sulfate compounds, for example. A further alternative is to made lens  30  about of a material containing a radioluminescent such as tritium, which glows in the dark but requires no external power inputs. For example, a tritium-embedded radioluminescent material may glow continuously and reliably for 10-20 years. 
     Light sources  13  may be Light Emitting Diodes (LEDs), incandescent bulbs, or any other suitable source. In an exemplary embodiment, a plurality of light sources (such as three light sources, as shown in  FIG. 2 ) are connected in series and electrically powered via conductors  60 ,  70 . In one exemplary embodiment, light sources  13  are LED bulbs emitting light in the visible wavelength range, such as 380-740 nm. Such bulbs can consume just 1.5-3.8 watts of energy and have a life expectancy of at least 10 years. 
     In another exemplary embodiment, light source  13  may be an LED configured to emit ultraviolet light, i.e., light having a wavelength between 10-400 nm. Such UV LED light sources provide UV charging light for the material of lens  30  directly from electrical power provided by conductors  60 ,  70 . Because UV light is the light wavelength which primarily acts to store energy in phosphors, this direct depositing of UV light into the phosphors embedded in lens  30  provides superior charging of the photoluminescent material. This provides faster and more robust “charging” of the material, thereby providing a longer and brighter discharge from lens  30 . In exemplary building systems utilizing sign assemblies  10 , UV light sources  13  can be provided at each location of cover plate  12 , thereby providing continuously charging of the material of lens  30  regardless of whether a typical ambient visible light source, such as an overhead light, is present or activated. Moreover, providing light source  13  within cavity  36  of lens  30 , and most clearly shown in  FIG. 3A , also provides the building operator with control over the time and manner of photon deposition into the material of lens  30 . This in turn ensures reliable and consistent discharge characteristics in case of a building emergency. 
     In yet other embodiments, a mixture of UV (i.e., non-visible) and conventional (i.e., visible) sources of light may be provided in the form of light sources  13 , such that the material of lens  30  is effectively and efficiently charged by the UV light source  13  while the visible-light source  13  illuminates lens  30  and makes indicia  20  easier to discern. 
     In still another alternative embodiment, light source  13  may be omitted from within cavity  36  defined by lens  30 . These applications might be appropriate for situations where sufficient ambient charging light is available, such as at least 54 LUX (5 ft-candles) of fluorescent, metal halide or mercury vapor light for 60-min. Such ambient-light-only applications might include emergency signs, as described herein, or may be nightlights which provide some illumination after room lights are extinguished. These applications carry advantages including minimal installation cost, zero power consumption, and maintenance-free operation. 
     For such non-powered applications, lens  30  may be omitted from sign assembly and backing plate  22  may be provided with embedded phosphors in a similar fashion as lens  30  described above. Thus, backing plate  22  may emit a glow from discharging photons, while also remaining flush with or recessed from outwardly facing surface  26  of cover plate  12 . 
     In certain exemplary embodiments, lens  30  is provided with a sign appliqué  20  attached thereto. In the illustrative embodiments of the  FIGS. 1A, 1B and 2 , for example, appliqué  20  is an “EXIT” sign with an arrow to point toward the nearest building exit. Sign assembly  10  having sign appliqué  20  may be mounted near the floor with duplex cover plate  12  at the interior of a building structure, as noted herein, to provide information to a viewer such as the location and direction of a the nearest building exit, or any other pertinent information. In an exemplary embodiment, appliqué  20  is applied as screened ink, though any method to apply visual indicia to outwardly facing lens surface  32  may be used such as painting, adhesive-backed coverings, and the like. Any color may be employed to achieve the desired visibility. 
     In an alternative embodiment, shown in  FIG. 4A , sign assembly  10 A may include cover plate  12 A. Cover plate  12 A is similar to cover plate  12  described above, and like reference numbers indicate like structures and features. However, cover plate  12 A includes switch aperture  40 A sized to receive a standard-sized electrical toggle switch of the type used to switch room lights on and off, instead of duplex outlet apertures  40  as shown in  FIG. 1A  with respect to cover plate  12 . For example, switch aperture may be 13/32-inches wide×1-inch tall, which advantageously fits a standard toggle switch of the type commonly used to turn room lights on and off in a building. 
     Cover plate  12 A also differs from cover plate  12  in that two sign apertures  50  are included. As illustrated, these two sign apertures  50  may be used to convey separate but related messages, such as by attaching exit sign lens  30  in one of apertures  50  and stairs sign lens  30 A in the other aperture  50 . Cover plate  12 A allows for lenses  30 ,  30 A to be mounted at a midpoint on a wall (such as wall W,  FIG. 5 ) to provide signage at the light-switch level. Advantageously, the typically higher mounting location of cover plate  12 A is substantially above the typical mounting location of cover plate  12 , and thereby avoids potential obstructions due to furniture, etc. 
     Advantageously, cover plates  12 ,  12 A can be provided as a system of signage for a building to convey information at any location suitable for a light switch or outlet. As such, sign assemblies  10 ,  10 A can be placed in any location where the direction of travel to the nearest exit is not apparent. A series of sign assemblies  10  and/or  10 A can be provided along a hallway, for example, such that occupants can see more than one sign at any one time and can follow the serial sign messages safely to a building exit. 
     As shown in  FIG. 4B , other standard cover plate arrangements  12 B- 12 E are amenable to use with lens  30 , backing plate  22  and/or the other structures described herein. Cover plate  12 B includes sign aperture  50  in combination with switch aperture  40 A, described above. Cover plate  12 C includes two sign apertures  50 , with one or both of apertures  50  usable to receive a lens in accordance with the present disclosure (e.g., one of lenses  30 ,  30 A described herein). Cover plate  12 D includes sign aperture  50  and two switch apertures  40 A. Cover plate  12 E includes only sign aperture  50 . Cover plates  12 ,  12 A,  12 B,  12 C,  12 D and/or  12 E may be used in any desired combination as a system of signage within a building. 
     Buildings especially suitable to use with sign assemblies  10 ,  10 A include hospitals and other medical facilities, college dormitories and other campus buildings, office buildings, and the like. Sign assemblies  10 ,  10 A are particularly helpful in building spaces where natural light is not available, such as underground areas or interior rooms including lavatories and storage rooms. 
     A method of installation of a sign assembly will now be described with reference to sign assembly  10 , it being understood that other sign assemblies made in accordance with the present disclosure may be installed in a similar fashion. First, lens  30  is assembled to backing plate  22  and backing plate  22  is in turn threadably connected to cover plate  12  using screws  16 ,  18 , as shown in  FIG. 2  and described in detail above. In the case of lens  30 , sign appliqué  20  bearing the “EXIT” sign is chosen and installed such that the arrow points to the nearest building exit. After connecting lens  30  to plate  12 , a sign assembly  10  is preassembled and ready for mounting to wall W as shown in  FIG. 5 . 
     In some cases, sign assembly  10  may be retrofitted to existing electrical infrastructure, and may even utilize the existing cover plates. In such cases, after disconnecting electrical power for safety, the existing cover plate may be removed from an underlying electrical access point  80  ( FIG. 5 ) disposed along interior wall W in a building. To make room for lens  30  and the associated structures, an electrical apparatus may be removed from either the existing cover plate  12 , if attached to the cover plate, or from junction box  82  of underlying electrical access point  80 . In an exemplary embodiment, lens  30  is sized to be received within sign aperture  50  which corresponds to a ground-fault circuit interrupt (GFCI) outlet or a standard “Decora” type panel switch as described above. Therefore, the removed electrical apparatus may be a GFCI outlet or panel switch. 
     When the chosen existing electrical apparatus is removed, an available space  84  is created that aligns with sign aperture  50  of cover plate  12  when cover plate  12  is mounted back upon junction box  82  at electrical access point  80 . 
     Wires  60  and  70  are then connected to the existing electrical infrastructure to provide power to light source(s)  13 . Such electrical connection is made by connecting wires  60 ,  70  to the electrical source of the building at source wires  61 ,  71  ( FIG. 5 ). In an exemplary embodiment, the positive one of wires  60 ,  70  should be connected to an “always energized” source wire  61  or  71  such that light source(s) are energized regardless of the state of any adjacent switch or outlet. When so connected, light source(s)  13  advantageously have a continuous supply of electrical current as long as the electrical infrastructure of the building is operational. 
     Cover plate  12  can then be mounted over junction box  82  at electrical access point. Mounting screw  14  may then be passed through mounting hole  15  formed in cover plate  12  and threaded into the underlying electrical apparatus (shown as standard duplex outlet  24 ) to attach cover plate  12 , together with lens  30  and backing plate  22 , to junction box  82 . When so mounted, cover plate covers electrical access point  80  and abuts wall W as shown in  FIG. 5 . Advantageously, because sign assembly  10  is provided on electrical cover plate  12 , electrical wires  60  and  70  may connected to the same electrical power source used for powering the electrical outlets  24  passing through apertures  40  of duplex cover plate  12 . 
     In addition cover plate  12  can be mounted to junction box using screws  16 ,  18  used to attach backing plate  22  to cover plate  12 . Screws  16 ,  18  may be provided in sufficient length to protrude beyond the back of cover plate  12 , such that screws  16 ,  18  may also thread into upper and lower threaded holes  86 ,  88 , respectively, formed in junction box  82 . 
     With sign assembly  10  now installed to electrical access point, electrical power may be activated to provide electrical power to light source(s)  13 . Advantageously, the above-described installation procedure can be accomplished by anyone with basic skills and equipment to wire an electrical outlet to existing electrical infrastructure. 
     While this disclosure has been described as having an exemplary design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.