Abstract:
A concealed safety light is described where the light source is integrated and mounted into a switch or power outlet wiring device. The light source is controlled by a circuit that detects ambient light and turns on the light source in the event of a power failure when it is dark. The resulting safety light is concealed in a standard wiring junction box and trimmed with conventional wall cover plate.

Description:
BACKGROUND OF INVENTION 
     1. Field of Invention 
     The present invention relates generally to alternate safety lighting devices and, more specifically, to an alternate safety lighting device that is combined with standard wall switches and power outlets such that they are unobtrusive and nearly indistinguishable from standard electrical wiring devices. 
     Emergency lighting devices are typically installed in such obvious ways that they interfere with visible design and decor of a living space or workspace. This often affects a person&#39;s decision whether or not to install them. By making the emergency lighting device inconspicuous, more installations and thus safer homes and workplaces will result. 
     Some amount of light is necessary during a night time power failure to allow people to move about safely. The reduction in size of high output light sources that consume small amounts of power, make integrating them into common devices possible without substantially altering the form and function of the original device. Sufficient light from these light emitting devices such as Light Emitting Diodes or Laser diodes allow people to see objects and pathways that might otherwise not be visible in the sudden darkness of a night time power failure. 
     Candles are often used during power failures that occur in the nighttime hours of darkness. The use of candles presents a fire safety risk and the present invention provides a safe alternative method of lighting an area to provide safe movement during such power failures. The present invention minimizes or eliminates the need for using candles during power blackouts. 
     2. Description of Prior Art 
     Similar prior art backup lighting devices that illuminate when a power failure occurs are often embodied in the form of a wall cover plate to surround an existing switch or AC outlet. Their embodiments are designed to mechanically and electrically attach to the switch or AC outlet either by direct attached wiring, plugs, or wireless means. Prior art devices do not disclose an apparatus concealed within a direct replacement for a common wall switch device or an AC outlet device. They also do not perceive or address the problem of being conspicuous, thus limiting the locations where one would install such devices. The present invention looks like and performs the function of the common wall switch or AC power outlet, installs into the standard electrical workboxes, and simultaneously provides the function of the safety light, thereby replacing the common wall switch or AC outlet entirely. It is concealed upon the installation of a standard wall cover plate over it and overcomes the problem of being conspicuous. 
     In U.S. Pat. No. 3,739,226 Seiter describes an emergency light for mounting to an electrical wall socket. The apparatus for emergency lighting plugs into an AC wall outlet. It is easily visible and conspicuous in its display and mounting mechanism. 
     In U.S. Pat. No. 4,514,789 Jester describes an illuminated light switch plate with LED and oscillator circuit to replace a wall cover plate. It is intended to locate the wall switch in the dark. It is a cover plate that has no power failure detection or backup lighting mechanism. 
     In U.S. Pat. Nos. 5,473,517, 5,713,655, and 6,010,228 Blackman describes a housing with an emergency safety lighting apparatus that replaces the wall cover plate and mechanically attaches to the wall switch device using the same screw mounting holes used by the former wall cover plate. It does not perform the function of the switch itself. It is large, plainly visible and protrudes from the wall as a result of its size, shape and the bulk of its housing. 
     In U.S. Pat. No. 5,833,350 and 6,000,807 Moreland describes a switch cover plate that houses the apparatus for emergency. In U.S. Pat. No. 4,631,649 McCue describes a plug-in emergency light fixture that plugs into a wall receptacle and is semi-permanently mounted by screwing it to the receptacle. None of these are part of the receptacle and they do not remain concealed or inconspicuous during the times when AC power is available. 
     Prior art generally discloses backup lighting devices that either plug into a power outlet or replace the cover plate that surrounds common AC wall switches and outlets. They do not disclose a concealed device that completely replaces the common wall switch or AC power outlet devices as in the present invention. The present invention occupies the same physical space, appears as and provides the function of a conventional switch or AC outlet, while simultaneously providing automatic illumination to an area when a power failure occurs resulting in a concealed safety lighting device. 
     The object of the present invention is to conceal the safety light source within the same physical housing used by a common switch or AC power outlet, thereby allowing the safety lighting device to be installed in very many locations inconspicuously. The device is installed in place of a conventional switch or outlet and provides emergency backup lighting with minimal visible impact on the design or decor of the area adjacent to the installed device. 
     SUMMARY OF INVENTION 
     The concealed safety lighting device is comprised of an electrical switch or power outlet, a detection mechanism connected to a primary power source for detecting the presence or lack of presence of the AC voltage, an alternate power source and a safety light source connected between the detection mechanism and the alternate power source. The detection mechanism monitors the availability of AC voltage and causes the safety light to illuminate upon detection of an interruption of the voltage at the terminals of the power source. The apparatus is capable of delivering sufficient illumination of the area adjacent to the installed device to allow safe movement and other activities in the area for periods of approximately 24 hours or more depending on the alternate power source selection The battery supplying power to the alternate safety light device may be rechargeable batteries where power failures are more frequent or non-rechargeable batteries where power failures may be infrequent, by implementing a simple change to the DC power circuitry. An integrated battery status indicator is optional. An integrated sensor adjusts the intensity of the safety light according to ambient lighting conditions thereby extending the battery life. 
     A primary object of the present invention is to provide an apparatus that is neither visible nor recognizable primarily as a device for providing alternate safety lighting and has little or no visible impact on interior space designs, thus overcoming the shortcomings of prior art devices. 
     Another object of the present invention is to provide an apparatus for providing alternate safety lighting for an extended period of time, while remaining smaller than most prior art. 
     Another object of the present invention is to provide an apparatus for providing alternate safety lighting that is able to detect the occurrence of a power failure. 
     An additional object of the present invention is to provide an apparatus for providing alternate safety lighting that is able to provide visibility from the concealed illumination device upon detection of a power failure, thereby allowing safe passage and mobility by persons in the nearby adjacent area. 
     A further object of the present invention is to provide an apparatus for providing alternate safety lighting including an indicator to warn the user of a low battery condition that would limit or prevent the device from illuminating during a power interruption due to a drained alternate power source. 
     A yet further object of the present invention is to provide an apparatus for providing alternate safety lighting to multiple unlit areas during power failures by installing in many locations throughout a house or building equipped with AC power in an inconspicuous manner. 
     A further object of the present invention is to provide a concealed safety lighting device that includes an ambient light detection mechanism for reducing the intensity of the emergency light when other light sources such as daylight are available to extend the life of the alternate power source during extended power outages. 
     A still further object of the present invention is to provide a concealed safety lighting device that includes an optional on/off switch for selectively turning the emergency light off during a power outage to conserve battery life if lighting is not needed in that area for a specific period of time. 
     Another object of the present invention is to provide a concealed safety lighting device that is activated and available for use with no specific action to be taken by the user. 
     A still further object of the present invention is to provide a concealed safety lighting device that is economical in cost to manufacture resulting in end user costs that imply affordability allowing for immediate commercial use. 
     An additional object of the present invention is to be easy to install with no additional knowledge necessary than that needed to install or replace common AC power outlets or switch devices. 
     Numerous devices for providing alternate safety lighting have been provided in the prior art. For example, U.S. Pat. Nos. 4,631,649, 5,473,517 and 5,833,350 all are illustrative of such prior art. While these units may be suitable for the particular purpose to which they address, they would not be as suitable for the purposes of the present invention as heretofore described. 
     Additional objects of the present invention will appear as the description proceeds. A concealed safety lighting device providing illumination of an area upon detection of the failure of the power source is disclosed by the present invention The light source is completely embodied in standard AC switches and power outlets. The concealed safety lighting device includes a power outlet or a switch, a detection circuit connected to the primary power source for detecting a voltage at terminals of the primary power source, an alternate power source and safety light source connected between the detection circuit and the alternate power source. 
     To the accomplishment of the above and related objects, this invention may be embodied in the form illustrated in the accompanying drawings, attention being called to the fact, however, that the drawings are illustrative only, and that changes may be made in the specific construction illustrated and described within the scope of the appended claims. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     Various other objects, features and attendant advantages of the present invention will become more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views. 
     FIG. 1A is a front view and FIG. 1B is a side view of the apparatus in the form of an AC switch for providing concealed safety lighting of the present invention, indicating the placement of high intensity light source in an inconspicuous manner. FIG. 1C shows a typical installation of the present invention in an electrical utility work box with the associated cover plate. 
     FIG. 2A is front view and FIG. 2B is a side view of the apparatus in the form of an AC power outlet for providing concealed safety lighting of the present invention. FIG. 2C shows a typical installation of the present invention in an electrical utility work box with the associated cover plate. 
     FIG. 3 is a cutaway view of the AC switch embodiment showing the integration of the standard switch and the emergency power failure backup lighting device components, the AC power outlet variation being substantially similar. 
     FIG. 4 is a reference design schematic diagram of a circuit of the apparatus for providing alternate safety lighting of the present invention. 
    
    
     DESCRIPTION OF THE REFERENCED NUMERALS 
     Turning now descriptively to the drawings, in which similar reference characters denote similar elements throughout the several views, the Figures illustrate the concealed safety lighting device in different embodiments of the present invention. With regard to the reference numerals used, the following numbering is used throughout the various drawing figures. 
       10 ,  10 ′. Safety light source. 
       11 . Normally exposed area of the switch visible after cover plate is installed. 
       12 . Normally exposed area of the outlet visible after cover plate is installed. 
       20 . Switch device housing containing switch mechanism and safety lighting apparatus 
       21 . Outlet device housing containing duplex power outlet mechanism and safety lighting apparatus. 
       30 , Clear or translucent body area to allow glow from indicator for low battery condition. 
       33 ,  33 ′. Light transmission means for safety light. 
       40 ,  40 ′. Ambient light detector. 
       50 ,  55 . On-Off-test switch. 
       60 . Battery Carrier. 
       70 . Alternate power source battery. 
       80 . External electrical connections. 
       90 . Circuit board containing the components necessary to implement the power failure backup lighting mechanism, control power monitoring and actuator circuits. 
       100 . Low battery warning indicator. 
       110 . Interior wall of device housing separating the low voltage circuit board and the AC voltage switch mechanism. 
       120 . Switch contacts. 
       130 . Outlet receptacle contacts. 
       140 . Switch Mounting bracket. 
       145 . Outlet Mounting bracket. 
       146 . Mounting holes. 
       147 . Screw 
       150 . Electrical utility work box 
       160 . Switch cover plate 
       165 . Outlet cover plate 
     DETAILED DESCRIPTION 
     Turning now descriptively to the drawings, in which similar reference characters denote similar elements throughout the several views, FIGS. 1A through 3 illustrate two implementations of the concealed safety lighting device of the present invention using classic styles of switches and outlets. Obvious implementations for the concealed safety lighting device using different styles of wiring devices such as decorative or Decora are not shown as they are substantially similar in their structure and function to conceal a safety lighting device. 
     FIGS. 1A through 1C show the safety light source  10  embodied in the normally exposed area of the switch  11  actuator handle in such a way as to allow the light to escape from the actuator handle through the light transmission means  33  which remains visible after installing the switch cover plate  160 . It also illustrates one method of installing the alternate power source battery  70  so to allow users to change them when necessary by removing the switch cover plate  160  and extracting the battery using the battery carrier  60 . The ambient light detector  40  is mounted in the normally exposed area of the switch  11  such a way as to sense surrounding light levels and adjust the level of power to the safety light source  10 . The switch device housing  20  is attached to switch mounting bracket  140  having all the standard structure to allow installation into a standard electrical utility work box  150  and conventional switch cover plate  160  using screws  147  into mounting holes  146 . The switch otherwise appears substantially the same as a standard AC switch when the conventional switch cover plate  160  is attached thereby covering the entire device installation. The external electrical connections  80  electrically connect to the switch contacts  120  providing normal AC switch function for the concealed safety lighting device. 
     FIGS. 2A through 2C show the safety light source  10 ′ embodied in the normally exposed area of the outlet  12  in such a way as to allow the light to escape through the light transmission means  33 ′, from the outlet face and through the conventional outlet cover plate  165 . The ambient light detector  40 ′ is mounted in the normally exposed area of the outlet  12  in such a way as to sense surrounding light levels and adjust the level of power to the safety light source  10  using screws  147  into mounting holes  146 . The outlet device housing  21  is attached to outlet mounting bracket  145  having all the standard structure to allow installation into a standard electrical utility work box  150  and conventional outlet cover plate  165 . The external electrical connections  80  are electrically connect to the outlet receptacle contacts  130  providing normal AC power outlet function for the concealed safety lighting device. 
     FIG. 3 shows a side cutaway view of the backup lighting mechanism in the form of a switch demonstrating one form that the body of the apparatus can take to contain all the components of the backup lighting device. The external electrical connections  80  enter the switch device housing  20  and connect to the circuit board  90  and to the switch contacts  120 . Wiring from the safety light source  10  and the ambient light detector  40  is routed through the interior wall  110  and connected to the circuit board  90 . Low battery warning indicator  100  is mounted in such a way as to protrude through the interior wall  110  to allow the clear or translucent body area  30  to glow and be visible to the user. Switch contacts  120  perform the same function as normal load-controlling switch contacts and are unremarkable. The switch device housing  20  is of sufficient size to contain all standard switch mechanics plus the power failure backup light mechanism herein described. 
     Emergency Lighting and AC Detection Circuit Operation Description. The following describes one design of how the alternate safety lighting detection and actuation reference design circuitry operate to provide necessary function as described in the present invention. Referring to FIG.  4 : AC Power Detection and DC Supply: This circuit represents a common transformer-less low power DC power supply design and may be implemented in other ways without impacting the scope of this present invention. 
     Battery Low Voltage Detector: Many devices are currently available to detect a voltage threshold and activate an indicator. This is one design to demonstrate how the present invention is able to incorporate the function. This circuit is optional and may be omitted without impacting the scope of the present invention. Diode D 3  prevents charging of replaceable batteries and is replaced with a current limiting mechanism when using rechargeable batteries. 
     Off Circuit: In this example circuit, transistor T 1  is held in the on state through resistor divider network R 4  and R 5  as long as AC is available. The output of T 1  will keep the safety light source  10 , in this reference example (LED D 4 ), in the off state by turning off transistor T 2 . Current flow while AC applied is supplied through D 2  through R 6 , through T 1 . In this reference example, ambient light detector  40  (CdS) has no function when AC is on since R 4  will hold T 1  on, T 2  off and safety light source  10  LED D 4  off. 
     When AC power is unavailable, transistor T 1  will control the brightness of the safety light source  10  (LED D 4 ) through the ambient light detector  40 , (CdS) which will develop a lower resistance as more light is detected. This raises the bias voltage on the base of transistor T 1  with respect to the amount of ambient light detected, thereby turning off D 4  and reducing current drain on the alternate power source battery  70  (B 1 ) to extend its useable life. 
     When AC power is available, transistor T 1  can optionally be used to control the brightness of the safety light source  10 , (LED D 4 ) through the ambient light detector  40 , CdS to provide a night light function by changing the value of the bias voltage at the base of T 1  to a value that allows transistor T 1  to turn off when a predetermined light level is reached. 
     Lighting control: The safety light source  10 , in this reference example a light emitting diode, D 4  will remain off while transistor T 2  is off. Resistor R 7  limits the amount of current through the (LED D 4 ) and is chosen to optimize light output and battery life. The optional on-off-test switch  50  will allow the safety light source  10  (LED D 4 ) to be deactivated if not needed during AC power failure conditions. The low voltage detector circuit is designed into the circuit in such a way as to trigger the low battery warning indicator  100  (D 1 ) when AC power is present and the battery voltage falls below a certain voltage determined by the resistor divider R 2 A and R 2 B. 
     The above circuit description is a reference design to indicate how one implementation can provide the necessary feature and function of the described present invention. 
     From the above description it can be seen that the concealed safety lighting device for providing alternate safety lighting of the present invention can be constructed in a small enough form factor to integrate the light source and the backup safety light mechanism into standard AC electrical switches and outlets to overcome the shortcomings of prior art devices. It describes a concealed safety lighting device that provides backup safety lighting in a concealed or inconspicuous way which is able to detect the occurrence of a power failure and provide backup safety lighting upon detection of the power failure. The backup safety light mechanism includes an alternate power source which can take the form of, but not limited to non-rechargeable batteries or rechargeable batteries with sufficient power density to provide a useful lighting period during utility supplied AC power failures. The backup safety light mechanism also includes an ambient light detector for extending the life of the batteries, and an optional on/off switch for selectively turning the emergency light off during a power outage. 
     Furthermore, the concealed safety lighting device of the present invention is simple and easy to install, use, and is economical to manufacture. It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of methods differing from the type described above. 
     While certain novel features of this invention have been shown and described using exemplary preferred embodiments, the scope of the invention is not intended to be limited to the details above, since it will be understood that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation can be made by those skilled in the art without departing in any way from the spirit of the present invention. Therefore, the scope of the claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.