Abstract:
A supplementary lighting device with a replaceable electroluminescent light element is disclosed. A control system is provided to boost the light intensity of the electroluminescent light element. A light sensor is provided which detects light emitted from the electroluminescent lighting element and inputs this information to the control system. The control system automatically adjusts the intensity of the electroluminescent lighting element according to a pre-set value and the information from the light sensor. This allows for the electroluminescent lighting element to maintain a constant output despite the ageing of the electroluminescent lighting element. The pre-set value for the intensity of the electroluminescent lighting element can be adjusted by a user controlled dimmer. The dimmer varies the amount of light detected by the light sensor in order to increase or decrease the power provided by the control system to the electroluminescent lighting element.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to supplementary lighting devices utilizing an electroluminescent lighting element and a control system. In particular, the present invention relates to an electronic and mechanical control system coupled to an electroluminescent lighting element in order to provide user-adjustable light intensity, automatic output compensation, and an automatic daytime shutoff feature. 
     2. Related Art 
     Supplementary lighting devices, such as night lights, are well known and commonly used for security and safety purposes. For example, supplementary lighting devices can be used to illuminate passageways and stairways to assist night travel or escape in an emergency. They are also commonly used to relieve night anxiety in children, decrease the probability of burglary, and may provide accent lighting. 
     Several different types of lighting elements can be used in supplementary lighting devices. For example, incandescent bulbs, fluorescent bulbs, neon-type gas discharge elements, and electroluminescent (EL) elements are possible lighting elements for supplementary lighting devices. When choosing a lighting element for a supplementary lighting device, several factors such as cost, safety, longevity, and illumination are generally taken into consideration. 
     Incandescent lighting elements offer low initial cost and are easily replaceable. Incandescent lighting elements also offer relatively bright light, which is preferable in security type applications. This bright light, however, is not desirable in night light type applications. Further, incandescent lights burn at very high temperatures. In a supplementary lighting type application, the bulbs are generally small such that the glass enclosure is close to the element. These supplementary lighting devices are generally located near the ground, within easy reach of small children. Therefore, incandescent lights create a safety risk to children. The point source emission of an incandescent light is less preferable than wide area emissions. 
     Neon type lighting elements could also be used in supplementary lighting devices. Neon lights are low cost. However, they are generally not user-replaceable, therefore the entire device must be discarded when the lighting element fails. Neon light elements, however, can last several years, although they initially have a precipitous rate of decline of output. Hence, the light they emit for most of their life is only a small fraction of their initial output. Neon lights are also generally dim. Neon lights are cool, thereby presenting less of a safety hazard than incandescent lights. 
     Fluorescent lighting elements are also used in supplementary lighting devices. Fluorescent lighting elements have a high initial cost, but can generally be replaced. However, because fluorescent lighting elements are generally difficult to find, supplementary lighting devices using them are generally throw-away type units. Fluorescent lighting elements produce a wide range of colors, and are generally very bright, without being a point source emission. Fluorescent lights are also generally cool, reducing the safety risk associated with hot lighting elements. Fluorescent lighting elements have a relatively long life span, but toward the end of their useful life, they often experience flickering of the lighting element. 
     Recently, electroluminescent (EL) lighting elements have become increasingly popular for use in supplementary lighting devices. EL lighting elements provide wide-area emission, are cool (i.e., will not burn to the touch), and have a very long life. Most EL lighting elements used in supplementary lighting devices are connected directly across the 110 volt, AC power from a common household outlet. However, these EL lighting elements have the disadvantage that they are generally dim, are not replaceable, and their intensity fades gradually over their life span. Additionally, EL lighting elements utilized in supplementary lighting devices also generally remain activated even during the day, when their relatively dim light is not required. 
     There exist well-known techniques for increasing the light intensity of EL lighting elements above that which is generated by connecting them across 110 AC power lines. Methods for increasing the output of EL lighting elements include altering the voltage, altering the oscillation frequency of the alternating electricity, varying the duty cycle, and/or varying the waveform. However, these methods for increasing the output EL lighting elements still suffer from some of the same drawbacks as conventional EL lighting elements. For example, power boosted EL lighting elements still suffer illumination declines over the life of the light. Further, the amount of light cannot be controlled for specific applications. 
     Supplementary lighting devices, regardless of the lighting element utilized, can also present a safety hazard to children due to their connection to a wall socket. These supplementary lighting devices are generally inserted into wall sockets located near the floor, within easy reach of small children. Children tend to play with the rear of the lighting device, where it is connected to the wall socket. Children can potentially burn themselves if they touch the blades of the supplementary lighting device while it is still connected to the wall socket. 
     SUMMARY OF THE INVENTION 
     As can be seen from the description above, there exists a need for a supplementary lighting device which includes the advantages of EL lighting elements while accounting for the disadvantages of such systems. 
     The present invention addresses these disadvantages by providing a supplementary lighting device with a user-adjustable dimmer that works in conjunction with a control system to vary the intensity of an EL lighting element. 
     The dimmer, preferably mechanically or optically, adjusts the amount of light detected by a light sensor from the EL lighting element. Therefore, by adjusting the dimmer, the amount of light actually detected by the light sensor is artificially varied, and the information from the light sensor is inputted into the control system, which then adjusts the amount of power provided to the EL lighting element in a closed loop feedback system. This arrangement simultaneously allows the control system to adjust for ageing of the EL lighting element. 
     Furthermore, the light sensor, or an additional one, may simultaneously detect ambient light, and depending on the amount of ambient light detected, the control system can completely shut off the EL lighting element. This provides a “daytime off” feature which conserves the EL lighting element and improves longevity of the device. 
     The EL lighting element is also replaceable. The device is designed such that a guide-way aligns the EL lighting element into mechanical and electrical contact with the control system. The guide-way is the only path from the user-accessible area of the device to the control system electronics. In addition, the device may be designed such that the EL lighting element is not accessible until the device is disconnected from a power source. In particular, the window covering the EL lighting element is coupled to the housing of the supplementary lighting device via a fastener which cannot be uncoupled without first disconnecting the device from the power source. This allows for safe replacement of the EL lighting element. 
     Another feature of the present invention is a safety device to prevent electrocution on electrical connection blades of the device while the device is still connected to a power source. In particular, a protector covers the electrical connection blades when the blades are removed from a power source. The protector retracts as the connection blades are inserted into a power source, and extends to cover the connection blades as the connection blades are removed from the power source. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     The present invention is described with reference to the accompanying drawings, wherein: 
     FIG. 1 is a functional block diagram of a supplementary lighting device of the present invention; 
     FIG. 2 is an isometric view of a supplementary lighting device of the present invention; 
     FIG. 3A is a front elevation view of a supplementary lighting device of the present invention; 
     FIG. 3B is a front elevation view of a supplementary lighting device of the present invention with the window removed; 
     FIG. 4 is an elevation view of an electroluminescent lighting element; 
     FIG. 5 is a cross-section of the supplementary lighting device of the present invention taken along lines  5 — 5  of FIG. 3A; 
     FIG. 6 is a rear elevation view of a supplementary lighting device of the present invention; 
     FIG. 7 is a side elevation of a supplementary lighting device of the present invention and a conventional wall socket; 
     FIGS. 8A and 8B are cross-section views of an embodiment of a dimmer of the present invention; 
     FIGS. 9A-9C are isometric views of an alternative embodiment of a dimmer of the present invention; 
     FIGS. 10A and 10B are a second alternative embodiment of a dimmer of the present invention; and 
     FIG. 11 is a block diagram of an embodiment of the control system of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A preferred embodiment of the present invention is now described with reference to the figures where like reference numbers indicate identical or functionally similar elements. Also in the figures, the left most digit of each reference number corresponds to the figure in which the reference number is first used. While specific configurations and arrangements are discussed, it should be understood that this is done for illustrative purposes only. A person skilled in the relevant art will recognize that other configurations and arrangements can be used without departing from the spirit and scope of the invention. 
     A preferred embodiment of a supplementary lighting device  100  is shown in block form in FIG.  1 . FIG. 1 shows that device  100  includes an illumination element  102 , light sensor  104 , a control system  106  and a dimmer  110 . Light sensor  104  and illumination element  102  are both coupled to control system  106 . Control system  106  is preferably an electronic system which receives input from light sensor  104  and controls illumination element  102 . Dimmer  110  is user controlled and varies the output intensity of illumination element  102  working in conjunction with light sensor  104 , illumination element  102  and/or control system  106 , as will be more fully explained below. 
     Illumination element  102  is an electroluminescent (EL) lighting element which will be described in more detail below. Light sensor  104  is preferably a light detecting resistor (LDR) and is disposed in device  100  so as to receive input both from illumination element  102  and any ambient light  108 . Light sensor  104  can also be configured as two light sensors, one for detecting light emitted from illumination element  102  and one for detecting ambient light  108 . Light sensor  104  can also be a photo-diode, photo-resistor, photo-transistor, or other similar devices which can detect light intensity. 
     Control system  106  is designed to generate an adjustable intensity of brightness of illumination element  102 . A preferred method of generating an adjustable intensity of brightness uses a combination of an astable oscillating circuit and a voltage multiplying circuit. The frequency of the oscillator is controlled by a pre-set signal as well as input received from light sensor  104 . In the example where light sensor  104  is an LDR, the resistance of the LDR is a function of the amount of light it receives. As the light intensity of ambient light  108  or illumination element  102  increases, the resistance of the LDR increases, thereby slowing the oscillator of control system  106 . As the oscillator slows, the intensity of illumination element  102  decreases. As would be apparent to one skilled in the relevant art, depending on the pre-set levels of control system  106 , illumination element  102  can be controlled such that when ambient light  108  is detected by light sensor  104  which is consistent with daylight or artificially lighted conditions, the oscillator is slowed such that illumination element  102  is turned “off.” 
     It can be appreciated that because light sensor  104  also receives light emitting from illumination element  102 , control system  106  acts as an intensity regulator to compensate for the decreased output of EL lighting elements due to aging. Therefore, with a pre-set intensity for illumination element  102 , as illumination element ages and its light intensity diminishes, light sensor  104  detects less light emitting from illumination element  102 . This information is transmitted to control system  106 , which increases the power to illumination element  102 . This provides an automatic intensity regulation feature which compensates for the effects of ageing in illumination element  102 . 
     FIG. 2 shows a preferred embodiment of supplementary lighting device  100 . Device  100  includes a housing  202 , a window  204 , and a dimmer control  206 . Dimmer control  206  allows the user to vary the pre-set intensity of illumination element  102 . Dimmer control  206  can allow the user to select in a variety of ways, as will be more fully described below. FIG. 3A shows a front elevation view of device  100 , showing housing  202 , window  204 , and dimmer control  206 . Light sensor  104  is also shown in phantom. FIG. 3B shows a front elevation of device  100  with window  204  removed. It can be seen that illumination element  102  is located behind window  204 . Light sensor  104  can also been seen in FIG.  3 B. Further, aperture  302  is located near light sensor  104  to allow detection of ambient light  108 . 
     A preferred embodiment of illumination element  102  is shown in FIG.  4 . Illumination element  102  includes a substantially planar illumination area  402  and an elongated connection tail  404  extending from illumination area  402 . Conductor strips  406  are disposed on connection tail  404 . Conductor strips  406  connect to control system  106  to provide power to illumination element  102 , as will be explained in more detail below. 
     FIG. 5 shows a side cross-section view of device  100 , taken along line  5 — 5  of FIG.  3 A. As can be seen, housing  202  and window  204  serve as an enclosure for device  100 . Window  204  is preferably coupled to housing  202  by a fastener  502  located at a rear surface  504  of housing  202 . Fastener  502  can be a screw or other similar type of fastening device. Window  204  may also be press fit into housing  202 . However, a fastener is a preferred attachment device. In particular, it is preferable that the fastener be located at rear surface  504  of housing  202 , because it requires removal of device  100  from the power source (wall socket) before window  204  can be removed. This safety precaution prevents one from attempting to replace illumination element  102  while device  100  is connected to the power source. 
     Window  204  preferably press fits illumination area  402  of illumination element  102  against a flat interior cavity  503  of housing  202 . Elongated tail  404  of illumination element  102  fits into a guide-way  505 . Guide-way  505  leads to connector  506  which connects to control system  106 . When elongated tail  404  is inserted through guide-way  505  and into connector  506 , conductor strips  406  make contact with connector  506 , such that control system  106  provides power to illumination element  102 . Guide-way  505  is the only path from the user-accessible area behind window  204  to control system  106 . 
     Also shown in FIG. 5 is an additional safety feature to prevent minor electrical shocks or burns to small children attracted to supplementary lighting device  100  due to its proximity to the ground and attractive light. Device  100  is normally plugged into a common household wall socket via electrical contact blades  508  which protrude from rear surface  504  of housing  202 . In a preferred embodiment of device  100 , a recess or cavity  510  is formed in rear surface  504  of housing  202  surrounding electrical contact blades  508 . A protector  512  is disposed in cavity  510  and extends the length of blades  508 . Protector  512  is collapsible such that it collapses into cavity  510  as blades  508  are inserted into the wall socket. When blades  508  are removed from the wall socket, protector  512  extends from cavity  510  to prevent contact with blades  508  until device  100  is completely removed from the wall socket. Protector  512  therefore prevents fingers, screwdrivers, toys, etc., from contacting blades  508  while blades are still in contact with the electrical power source. Protector  512  is preferably made of nonconductive and resilient material such as rubber, and is preferably constructed in the form of bellows, as shown, for easy expansion and contraction. 
     FIG. 6 shows an elevation view of rear surface  504  of device  100 , including cavity  510 , electrical connection blades  508 , and fasteners  502 . FIG. 7 shows a side elevation of device  100  coupled to a standard household outlet  702  as a power source. 
     Explanation will now be provided for various embodiments of dimmer  110 . Dimmer  110  can vary the illumination intensity of illumination element  102  by directly acting with control system  106 , as shown in FIG.  1 . Preferably, however, dimmer  110  works in conjunction with light sensor  104  to mechanically and/or optically adjust the intensity of light output from illumination element  102  which is detected by light sensor  104 . As discussed above, the intensity of light outputted from illumination element  102  is increased or decreased by control system  106  depending on the amount of light detected from light sensor  104 . Therefore, dimmer  110  is constructed such that the amount of light detected by light sensor  104  can be artificially adjusted by the user. 
     One embodiment of a dimmer  110  is shown in FIGS. 8A and 8B. In this preferred embodiment, dimmer  110  comprises dimmer control  206  constructed as a small wheel which can be adjusted by the user. Light sensor  104  is disposed within wheel dimmer control  206  such that when dimmer control  206  is moved, light sensor  104  is angled towards or away from illumination element  102 . When light sensor  104  is angled away from illumination element  102 , as shown in FIG. 8B, it detects less light from illumination element  102 , thereby causing control system  106  to increase power to illumination element  102 , to make increase the intensity of illumination element  102  until the system regulates itself. Conversely, when dimmer control  206  is moved in the other direction, as shown in FIG. 8A, light sensor  104  is angled towards illumination element  102 , thereby detecting more light from illumination element  102 . Consequently, control system  106  reduces power to illumination element  102  which dims the output. It would be apparent to one skilled in the relevant art from this description that light sensor  104  also moves slightly closer to and away from illumination element  102  when dimmer control  206  is moved. This further increases or decreases the amount of light detected by light sensor  104 . It can further be appreciated that if light sensor  104  is moved away from the center of dimmer control  206 , turning dimmer control  206  towards or away from illumination element  102  has a greater effect on the distance that light sensor  104  moves towards or away from illumination element  102 . 
     Another embodiment of dimmer  110  is shown in FIGS. 9A-9C. In this embodiment, dimmer  110  comprises dimmer control  206  and a mechanical dimmer element constructed as a sloped section  904 . Dimmer control  206  allows the user to slide sloped section  904  such that light sensor is progressively unblocked (FIG.  9 A), partially blocked (FIG.  9 B), or completely blocked (FIG.  9 C). The amount of sloped section  904  blocking light sensor  104  adjusts the quantity of light detected by light sensor  104 . Therefore, if dimmer control  206  is moved such that sloped section  904  completely blocks light sensor  104 , light sensor  104  detects no light from illumination element  102 , thereby causing control system  106  to increase power to illumination element  102 . Similarly, as dimmer control  206  is moved such that sloped section  904  begins to uncover light sensor  104 , light sensor  104  detects more light from illumination element  102 . This causes control system  106  to decrease power to illumination element  102 , thereby decreasing the intensity of light emitted from illumination element  102 . 
     FIGS. 10A and 10B show another alternative embodiment of dimmer  110 . In this embodiment, dimmer  110  comprise a dimmer control  206  and a partially mirrored reflective section  1002 . Reflective section  1002  has a sloped reflective surface across its face. Dimmer control  206  allows the user to slide reflective section  1002  such that light emitted from illumination element  102  is variably reflected as a function of the amount of reflective material on the part of reflective section  1002  which is positioned so as to conduct light to light sensor  104  via aperture  1004 . The sliding position of dimmer control  206  therefore adjusts the quantity of light detected by light sensor  104 . As described above, if dimmer control  206  is moved such that reflective section  1002  reflects effectively no illumination from illumination element  102 , light sensor  104  detects no light from illumination element  102 , thereby causing control system  106  to increase power to illumination element  102 . Similarly, as dimmer control  206  is moved such that reflective section  1002  reflects a greater amount of light from illumination element  102 , light sensor  104  detects more light from illumination element  102 . This causes control system  106  to decrease power to illumination element  102 , thereby decreasing the intensity of light emitted from illumination element  102 . 
     Several other possible embodiments of dimmer  110  exist. For example, dimmer control  206  could be coupled to illumination element  102  such that moving dimmer control  206  moves illumination element  102  towards or away from light sensor  104 . This has the same effect as moving light sensor  104  towards or away from illumination element  102 , as described above with respect to FIGS. 8A and 8B. Similarly, an adjustable reflecting device could be positioned between illumination source  102  and light sensor  104 . Dimmer control  206  adjusts the angle or position of the reflecting device such that light sensor  104  detects more or less light from illumination element  102 . Several other similar devices could be designed that increase or decrease the amount of light detected by light sensor  104  from illumination element  102 . 
     Note that dimmer  110  can be designed to completely shut off light from illumination source  102  to light detector  104 , as discussed above. This would allow maximum light output from illumination source  102 , and also provides for the greatest amount of variability in output power (i.e., from 0% to 100%). It is also possible to design dimmer  110  such that it cannot completely prevent light from illumination source  102  from reaching light detector  104 . In this embodiment, the system could not produce maximum output of the illumination source, however, it could provide automatic decay adjustment over a longer period of the illumination element&#39;s life span. For example, the system could be designed such that when dimmer  110  is adjusted for maximum output, control system  106  would only provide 30% of its maximum power supplying capability to illumination element  102 . Although the maximum light output of such a system is initially less than if 100% of the power supplying capability were utilized, as illumination element  102  ages, the remaining 70% of control system&#39;s  106  power supplying capability would steadily come into effect. This would allow illumination element  102  to keep is artificial “maximum” output for a longer period of time. 
     An exemplary embodiment of control system  106  is shown in block diagram form in FIG.  11 . As would be apparent to one of ordinary skill in the relevant art, this is only a particular embodiment of control system  106 . Several other designs could be utilized to achieve the same or similar result. Control system  106  receives input from AC power source  1102  and from light sensor  104 . AC power is then treated through a rectifier  1104  and a power conditioner  1106 . Rectifier  1104  can be a full wave rectifier, a half wave rectifier, a voltage doubler, or several other common design alternatives. Power conditioner  1106  can be comprised of capacitors, or resistors and capacitors, or inductors and capacitors, or various other common implementations. The purpose of power conditioner  1106  is to provide some amount of stabilization for the rectified power source. An oscillator  1108  receives the rectified and conditioned A/C power. Oscillator  1108  can generate a sinusoidal wave via an RC shift network, a Wien bridge, or an inductor-capacitor arrangement. Alternatively, oscillator  1108  can could generate a modified square wave or a composite wave-form via flip-flops, or an astable network, or via a free-running multi-vibrator, or via several other common circuit implementations, as would be apparent to one of ordinary skill in the relevant art. Oscillator  1108  could also use crystal or ceramic oscillators, or even the output of a microprocessor. Oscillator  1108  can be designed as either a fixed- or variable-controlled oscillator. If the design is a variable-controlled oscillator, then the conditioned signal from light sensor  104  can vary the rate of oscillation as a function of the amount of light sensed, and thus it would affect the intensity of the EL element. 
     The output of the oscillator  1108  is then sent to a power adjuster  1110  which conditions the output so that it is within the operating norms of illumination element  102 . The resulting power is then output from control system  106  and applied to the contacts of the EL lighting element, producing an appropriate glow. Power adjuster  1110  can be either a fixed- or variable-controlled regulator design, configured so as to adjust either the voltage or the current (or both). If the design is a variable-controlled regulator, then the conditioned signal from light sensor  104  varies the amount of power output during each oscillation as a function of the amount of light sensed, and thus it would affect the intensity of illumination element  102 . 
     The second input into control system  106  is from light sensor  104 . The input from light sensor  104  is conditioned by conditioner  1112  to adjust it to the needs of the other circuitry in control system  106 . The output from conditioner  1112  is then applied as a controlling signal for either oscillator  1108  or power adjuster  1110 , or both. Thus, the signal from light sensor  104  affects the intensity of illumination element  102 . 
     As the intensity of illumination element  102  varies, the changed intensity from illumination element  102  is detected by light sensor  104  transferred to control system  106 , as described above. This allows for constant adjustment of the intensity of illumination element  102  to a desired setting, even when illumination element  102  begins to fade. As fading begins to occur, light sensor  104  will detect less light from illumination element  102 , and power adjuster  1110  or oscillator  1108  of control system  106  will thereby increase the intensity of illumination element  102  until it reaches the intensity pre-set by the user using dimmer control  206 . Similarly, as dimmer control  206  is adjusted, light sensor  104  detects less or more light from illumination element  102 . Control system  106  automatically adjusts for this change, and power adjuster  1110  provides more or less power to illumination element  102 . This allows for user control of the intensity of illumination element  102  simply by adjusting dimmer control  206 . 
     In addition, when light sensor  104  is designed to detect ambient light  108  from the area surrounding device  100 , an increase in ambient light  108  will cause control system  106  to decrease the intensity of illumination element  102 . Therefore, control system  106  can be designed such that the amount of ambient light  108  detected by light sensor  104  will be sufficient to completely shut off illumination element  102  in daylight type conditions. This provides a “daytime off” feature which extends the serviceable life of illumination element  102 . Similarly, light sensor  104  can be designed such that it receives both ambient light and light emitted from illumination element  102 . Control system  106  can be designed such that the amount of ambient light  108  detected by light sensor  104  exceeds the amount of light detected from illumination element  102 . Further, dimmer  110  can be designed to affect only that amount of light detected by light sensor  104  which is emitted by illumination element  102 . This combination of design element allows the anti-ageing feature, the daytime-off feature, and the adjustable dimmer feature to be efficiently incorporated into a supplementary lighting device. 
     While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.